Added storage bucket datasource

[shuyama1]

This resolves hashicorp/terraform-provider-google#5311

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

`google_storage_bucket`

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 5 files changed, 107 insertions(+))
Terraform Beta: Diff ( 7 files changed, 110 insertions(+), 2 deletions(-))

[c2thorn]

maybe the VCR tests timed out?

[c2thorn]

/gcbrun

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 5 files changed, 107 insertions(+))
Terraform Beta: Diff ( 5 files changed, 107 insertions(+))

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceGoogleStorageBucket_basic|TestAccComputeForwardingRule_update You can view the result here: https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=208304

[rileykarson]

Watch out for the test / lint checks prior to merging! VCR failing for no good reason has definitely given me a bad habit of dismissing red checks- I think one of the files needs a make fmt is all.

[shuyama1]

Thanks for pointing it out! Working on it.

[rileykarson]

Added you on #5255, running gofmt -w mmv1/third_party/terraform/tests/data_source_google_storage_bucket_test.go it took to fix. Just a picky linter!

[shuyama1]

Thanks!