Revert "Reimplemented compute service attachment using the DCL (#5342)"

[rileykarson]

This reverts commit b932c48. /cc @trodge

I don't think that this PR was ready to merge, and believe that it introduced multiple breaking changes to the provider in addition to major regressions in terms of documentation. Before moving forward with a replacement for the PR I'd request the following are resolved:

• google_compute_forwarding_rule.project lost a diff suppress func. This one would have widespread negative impact, as the previous implementation of the resource stored the long form of the project in state even if the user specified the short form.
• google_compute_global_forwarding_rule.project has the exact same change, with similar impact.
• google_compute_forwarding_rule.region lost a DSF in a similar vein to FR/GFR project
• google_compute_service_attachment.name lost the ForceNew property. This field is extemely unlikely to be updatable. If it is, that's worth explaining in the migration PR.
• google_compute_service_attachment's documentation was deleted
• google_cloudbuild_worker_pool.project lost a diff suppress func. This one is unlikely to have widespread impact as the value specified in config is the stored value, but switching project formats would have caused a diff when it did not previously.
• google_dataproc_workflow_template.project lost a DSF, with similar impact to above.
• google_eventarc_trigger.project lost a DSF, with similar impact to above.
• google_gke_hub_feature lost a DSF.project, with similar impact to above.
• google_gke_hub_feature_membership.project lost a DSF, with similar impact to above.
• google_privateca_ca_template.project lost a DSF, with similar impact to above.
• google_compute_service_attachment.nat_subnets had a change in schema (I'm unsure if they are compatible- we should avoid these kinds of changes in the initial move to the DCL.

Possibly harmless, but also worth resolving:

• google_compute_service_attachment.consumer_accept_lists.connection_limit went from required -> optional w/ no justification
• google_compute_service_attachment.enable_proxy_protocol went from required -> optional w/ no justification
• google_compute_service_attachment.fingerprint has a misleading description, implying that end users will need to specify it. They cannot.
• google_compute_service_attachment.service_attachment_id does not appear to be returned by the API

Additionally, I think we'll want to improve the documentation as was done in #5325 for this or any other brownfield resource. I believe this requires manual work in the DCL.

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)

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 15 files changed, 1127 insertions(+), 664 deletions(-))
Terraform Beta: Diff ( 18 files changed, 1145 insertions(+), 679 deletions(-))
TF Validator: Diff ( 1 file changed, 11 deletions(-))

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDatasourceGoogleServiceNetworkingPeeredDnsDomain_basic|TestAccCloudFunctionsFunction_vpcConnector|TestAccComputeInstanceFromMachineImage_basic|TestAccComputeInstanceFromMachineImage_overrideMetadataDotStartupScript|TestAccComputeInstanceFromMachineImage_diffProject|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupAppengineExample|TestAccComputeServiceAttachment_serviceAttachmentBasicExampleUpdate|TestAccServiceNetworkingPeeredDNSDomain_basic|TestAccSqlUser_postgresIAM You can view the result here: https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=217246

[modular-magician]

Tests failed during RECORDING mode: TestAccComputeInstanceFromMachineImage_overrideMetadataDotStartupScript|TestAccComputeInstanceFromMachineImage_basic|TestAccComputeInstanceFromMachineImage_diffProject|TestAccCloudFunctionsFunction_vpcConnector|TestAccComputeRegionNetworkEndpointGroup_regionNetworkEndpointGroupAppengineExample|TestAccSqlUser_postgresIAM Please fix these to complete your PR