Add mutex to compute_project_metadata_item

[ct-dh]

This PR resolves issue hashicorp/terraform-provider-google#9119 on the terraform provider. Adding a mutex to the compute_project_metadata_item resource means that the provider will not fight itself when applying updates to the common instance metadata (which use optimistic locking). A longer term solution would be to implement batching.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

compute: added mutex in `google_compute_metadata_item` to reduce retries + quota errors

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[modular-magician]

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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 4 insertions(+))
Terraform Beta: Diff ( 2 files changed, 6 insertions(+), 1 deletion(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=186823"

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 4 insertions(+))
Terraform Beta: Diff ( 2 files changed, 5 insertions(+), 2 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=187002"

[ScottSuarez]

/gcbrun

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=187866"

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 4 insertions(+))
Terraform Beta: Diff ( 2 files changed, 6 insertions(+), 1 deletion(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=187867"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccContainerClusterDatasource_zonal|TestAccContainerClusterDatasource_regional|TestAccBigQueryDataTable_bigtable|TestAccCloudIdentityGroup_update|TestAccComputeAddress_internal|TestAccComputeInstanceTemplate_subnet_auto|TestAccComputeInstanceTemplate_subnet_custom|TestAccComputeInterconnectAttachment_interconnectAttachmentBasicExample|TestAccComputeNetworkPeeringRoutesConfig_networkPeeringRoutesConfigGkeExample|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupAppengineExample|TestAccContainerCluster_basic|TestAccContainerCluster_misc|TestAccContainerCluster_withNotificationConfig|TestAccContainerCluster_withAddons|TestAccContainerCluster_withMasterAuthConfig|TestAccContainerCluster_withNetworkPolicyEnabled|TestAccContainerCluster_withMasterAuthConfig_NoCert|TestAccContainerCluster_withTelemetryEnabled|TestAccContainerCluster_withReleaseChannelEnabled|TestAccContainerCluster_withAuthenticatorGroupsConfig|TestAccContainerCluster_withMasterAuthorizedNetworksConfig|TestAccContainerCluster_withReleaseChannelEnabledDefaultVersion|TestAccContainerCluster_regional|TestAccContainerCluster_regionalWithNodeLocations|TestAccContainerCluster_regionalWithNodePool|TestAccContainerCluster_withTpu|TestAccContainerCluster_withIntraNodeVisibility|TestAccContainerCluster_withPrivateClusterConfig|TestAccContainerCluster_withNodeConfig|TestAccContainerCluster_withVersion|TestAccContainerCluster_withNodeConfigScopeAlias|TestAccContainerCluster_withNodeConfigShieldedInstanceConfig|TestAccContainerCluster_withSandboxConfig|TestAccContainerCluster_withWorkloadMetadataConfig|TestAccContainerCluster_withNodePoolBasic|TestAccContainerCluster_withNodePoolAutoscaling|TestAccContainerCluster_withNodePoolResize|TestAccContainerCluster_network|TestAccContainerCluster_backend|TestAccContainerCluster_withNodePoolMultiple|TestAccContainerCluster_withNodePoolNodeConfig|TestAccContainerCluster_withMaintenanceWindow|TestAccContainerCluster_withRecurringMaintenanceWindow|TestAccContainerCluster_withMaintenanceExclusionWindow|TestAccContainerCluster_withIPAllocationPolicy_existingSecondaryRanges|TestAccContainerCluster_withIPAllocationPolicy_specificIPRanges|TestAccContainerCluster_withIPAllocationPolicy_specificSizes|TestAccContainerCluster_nodeAutoprovisioning|TestAccContainerCluster_nodeAutoprovisioningDefaults|TestAccContainerCluster_withWorkloadIdentityConfig|TestAccContainerCluster_nodeAutoprovisioningDefaultsMinCpuPlatform|TestAccContainerCluster_withAutoscalingProfile|TestAccContainerCluster_withBinaryAuthorization|TestAccContainerCluster_errorNoClusterCreated|TestAccContainerCluster_withFlexiblePodCIDR|TestAccContainerCluster_errorCleanDanglingCluster|TestAccContainerCluster_withDatabaseEncryption|TestAccContainerCluster_withAdvancedDatapath|TestAccContainerCluster_withResourceUsageExportConfig|TestAccContainerCluster_withEnableKubernetesAlpha|TestAccContainerCluster_withMasterAuthorizedNetworksDisabled|TestAccContainerNodePool_basic|TestAccContainerNodePool_withNodeConfig|TestAccContainerNodePool_nodeLocations|TestAccContainerNodePool_maxPodsPerNode|TestAccContainerNodePool_withWorkloadIdentityConfig|TestAccContainerNodePool_withLinuxNodeConfig|TestAccContainerNodePool_withSandboxConfig|TestAccContainerNodePool_withKubeletConfig|TestAccContainerNodePool_withUpgradeSettings|TestAccContainerNodePool_withManagement|TestAccContainerNodePool_withInvalidUpgradeSettings|TestAccContainerNodePool_withGPU|TestAccContainerNodePool_withNodeConfigScopeAlias|TestAccContainerNodePool_regionalAutoscaling|TestAccContainerNodePool_autoscaling|TestAccContainerNodePool_EmptyGuestAccelerator|TestAccContainerNodePool_resize|TestAccContainerNodePool_012_ConfigModeAttr|TestAccContainerNodePool_shieldedInstanceConfig|TestAccContainerNodePool_regionalClusters|TestAccContainerNodePool_ephemeralStorageConfig|TestAccDNSManagedZone_privateUpdate|TestAccDNSPolicy_update|TestAccGKEHubMembership_gkehubMembershipIssuerExample|TestAccGKEHubMembership_gkehubMembershipBasicExample You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=187872"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccBigQueryDataTable_bigtable You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=187874"