Added services monitoring data sources

[edwardmedia]

Fixes hashicorp/terraform-provider-google#6429

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)

`google_monitoring_cluster_istio_service`
`google_monitoring_mesh_istio_service`

[edwardmedia]

No tests are added in this PR as currently there is no TF-supported method that can be used to enable both services (Cluster Istio and Mesh Istio) in GKE

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 6 files changed, 297 insertions(+))
Terraform Beta: Diff ( 6 files changed, 297 insertions(+))

[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=157304"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceSpannerInstance_basic|TestAccApiGatewayApiConfigIamBindingGenerated|TestAccApiGatewayApiConfigIamMemberGenerated|TestAccApiGatewayApiConfigIamPolicyGenerated|TestAccApiGatewayGatewayIamBindingGenerated|TestAccApiGatewayGatewayIamMemberGenerated|TestAccApiGatewayGatewayIamPolicyGenerated|TestAccApiGatewayApiConfig_apigatewayApiConfigBasicExample|TestAccApiGatewayApiConfig_apigatewayApiConfigBasicExampleUpdated|TestAccApiGatewayGateway_apigatewayGatewayBasicExample|TestAccApiGatewayGateway_apigatewayGatewayBasicExampleUpdated|TestAccActiveDirectoryDomainTrust_activeDirectoryDomainTrustBasicExample|TestAccBigqueryDataTransferConfig|TestAccComposerEnvironment_withUpdateOnCreate|TestAccFilestoreInstance_filestoreInstanceBasicExample|TestAccFilestoreInstance_update|TestAccOSLoginSSHPublicKey_osLoginSshKeyExpiry|TestAccStorageBucket_cors You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=157309"

[ScottSuarez]

lgtm... adding @ndmckinley for a second pass.

[nat-henderson]

Understood why there's no test - can you add a note for us for the future somewhere? Maybe in a comment in the resource, that would do it? Other than that, LGTM.

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 6 files changed, 301 insertions(+))
Terraform Beta: Diff ( 6 files changed, 301 insertions(+))

[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=158655"

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 6 files changed, 301 insertions(+))
Terraform Beta: Diff ( 6 files changed, 301 insertions(+))

[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=158656"

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 6 files changed, 301 insertions(+))
Terraform Beta: Diff ( 6 files changed, 301 insertions(+))

[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=158671"

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 6 files changed, 301 insertions(+))
Terraform Beta: Diff ( 6 files changed, 301 insertions(+))

[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=158674"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceSpannerInstance_basic|TestAccApiGatewayApiConfigIamBindingGenerated|TestAccApiGatewayApiConfigIamMemberGenerated|TestAccApiGatewayApiConfigIamPolicyGenerated|TestAccApiGatewayGatewayIamMemberGenerated|TestAccApiGatewayGatewayIamBindingGenerated|TestAccApiGatewayGatewayIamPolicyGenerated|TestAccApiGatewayApiConfig_apigatewayApiConfigBasicExample|TestAccApiGatewayApiConfig_apigatewayApiConfigBasicExampleUpdated|TestAccApiGatewayGateway_apigatewayGatewayBasicExample|TestAccApiGatewayGateway_apigatewayGatewayBasicExampleUpdated|TestAccActiveDirectoryDomainTrust_activeDirectoryDomainTrustBasicExample|TestAccBigtableAppProfile_bigtableAppProfileMulticlusterExample|TestAccBigtableAppProfile_bigtableAppProfileSingleclusterExample|TestAccBigqueryDataTransferConfig|TestAccComposerEnvironment_withUpdateOnCreate|TestAccFilestoreInstance_filestoreInstanceBasicExample|TestAccFilestoreInstance_update|TestAccLoggingOrganizationSink_described|TestAccLoggingOrganizationSink_disabled|TestAccOSLoginSSHPublicKey_osLoginSshKeyExpiry You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=158675"