Filestore: zonal tier support

[bsteinberg]

Zonal tier support for Filestore.

Release Note Template for Downstream PRs (will be copied)

filestore: added support for the `"ZONAL"` value to `tier` in `google_filestore_instance`

[modular-magician]

Hello! I am a robot. It looks like you are a: Community Contributor Googler Core Contributor. Tests will run automatically.

@rileykarson, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 2 files changed, 4 insertions(+), 4 deletions(-))
Terraform Beta: Diff ( 2 files changed, 4 insertions(+), 4 deletions(-))

[modular-magician]

Tests analytics

Total tests: 3065
Passed tests 2766
Skipped tests: 299
Affected tests: 0

$\textcolor{green}{\textsf{All tests passed in REPLAYING mode.}}$
View the build log

[rileykarson]

This already worked for new resources since we don't validate the value anymore, but adding to release notes anyways in case users were unaware.