Add validation for Composer max pods per node field

[gor-obr]

Add validation for Composer max pods per node field (must be an integer between 8 and 110).

part of hashicorp/terraform-provider-google#9346

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)

composer: added validation for `max_pods_per_node` field.

[modular-magician]

Oops! It looks like you're using an unknown release-note type in your changelog entries:

• enchancement

Please only use the types listed in https://github.com/GoogleCloudPlatform/magic-modules/blob/master/.ci/RELEASE_NOTES_GUIDE.md.

[modular-magician]

Hello! I am a robot who works on Magic Modules PRs.

I have detected that you are a community contributor, so your PR will be assigned to someone with a commit-bit on this repo for initial review.

Thanks for your contribution! A human will be with you soon.

@rileykarson, please review this PR or find an appropriate assignee.

[modular-magician]

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

Diff report:

Terraform Beta: Diff ( 1 file changed, 6 insertions(+), 5 deletions(-))

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccAssuredWorkloadsWorkload_basic|TestAccAssuredWorkloadsWorkload_full|TestAccBigqueryDataTransferConfig|TestAccBigqueryReservationReservation_bigqueryReservationBasicExample|TestAccBillingBudget_budgetFilterProjectsOrdering|TestAccBillingBudget_billingBudgetUpdate|TestAccCloudBuildTrigger_pubsub_config|TestAccCloudBuildTrigger_webhook_config|TestAccComposerEnvironment_withMaintenanceWindow|TestAccComputeBackendService_withBackend|TestAccComputeBackendService_withBackendAndIAP|TestAccComputeBackendService_withBackendAndMaxUtilization|TestAccComputeBackendService_withMaxConnections|TestAccComputeBackendService_withMaxConnectionsPerInstance|TestAccComputeBackendService_withMaxRatePerEndpoint|TestAccComputeBackendService_withMaxConnectionsPerEndpoint|TestAccComputeGlobalForwardingRule_globalForwardingRuleInternalExample|TestAccComputeGlobalForwardingRule_internalLoadBalancing|TestAccComputeHaVpnGateway_computeHaVpnGatewayEncryptedInterconnectExample|TestAccComputeInstanceGroup_rename|TestAccComputeRouter_computeRouterEncryptedInterconnectExample|TestAccContainerCluster_backend|TestAccContainerNodePool_withGPU|TestAccDataLossPreventionDeidentifyTemplate_dlpDeidentifyTemplateBasicExample|TestAccDataLossPreventionDeidentifyTemplate_dlpDeidentifyTemplateUpdate|TestAccDialogflowCXFlow_dialogflowcxFlowFullExample|TestAccDialogflowCXVersion_dialogflowcxVersionFullExample|TestAccDialogflowCXFlow_update|TestAccDialogflowCXVersion_update|TestAccGKEHubMembership_gkehubMembershipBasicExample|TestAccGKEHubMembership_gkehubMembershipIssuerExample|TestAccNetworkServicesEdgeCacheKeyset_networkServicesEdgeCacheKeysetBasicExample|TestAccNetworkServicesEdgeCacheOrigin_networkServicesEdgeCacheOriginBasicExample|TestAccNetworkServicesEdgeCacheOrigin_networkServicesEdgeCacheOriginAdvancedExample|TestAccNetworkServicesEdgeCacheOrigin_updateAndImport|TestAccNetworkServicesEdgeCacheService_networkServicesEdgeCacheServiceBasicExample|TestAccNetworkServicesEdgeCacheService_networkServicesEdgeCacheServiceAdvancedExample|TestAccNetworkServicesEdgeCacheService_updateAndImport|TestAccPrivatecaCertificate_privatecaCertificateCsrExample|TestAccPrivatecaCertificateAuthority_privatecaCertificateAuthorityBasicExample|TestAccPrivatecaCertificate_privatecaCertificateConfigExample|TestAccPrivatecaCertificate_privatecaCertificateNoAuthorityExample|TestAccSecurityCenterNotificationConfig_sccNotificationConfigBasicExample You can view the result here: https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=198232

[modular-magician]

Tests failed during RECORDING mode: TestAccDataLossPreventionDeidentifyTemplate_dlpDeidentifyTemplateBasicExample|TestAccGKEHubMembership_gkehubMembershipBasicExample|TestAccGKEHubMembership_gkehubMembershipIssuerExample|TestAccNetworkServicesEdgeCacheOrigin_networkServicesEdgeCacheOriginAdvancedExample Please fix these to complete your PR