Made project_service.service validation reject invalid service domains

[melinath]

Resolved hashicorp/terraform-provider-google#8875

There are a variety of supported domains (and more may be added). I think adding a simple check for the domain being plausible (i.e. "does it contain a period") should catch simple typos like the one in the linked issue while also being future-proof.

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.
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Release Note Template for Downstream PRs (will be copied)

serviceusage: Made `google_project_service.service` validation reject invalid service domains that don't contain a period

[melinath]

/gcbrun - failure was unrelated

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 2 files changed, 54 insertions(+), 1 deletion(-))
Terraform Beta: Diff ( 2 files changed, 54 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=183635"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccComputeBackendService_internalLoadBalancing You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=183637"