Add google_datastream_static_ips data source

[modular-magician]

This PR introduces a google_datastream_static_ips data source, enabling automated access to the Datastream IP allowlists via the projects.locations.fetchStaticIps API method.

This is similar to the google_monitoring_uptime_check_ips data source (#3320), except that the API method requires a name parameter passing to it, which is constructed from project and location (projects/{project}/locations/{location}).

The data source therefore accepts project and location as inputs. project is optional, as that can be inferred from the provider configuration. location is required however as, whilst it could be inferred through getLocation, it's not appropriate to infer it because:

• getLocation can fall back to a zone argument, whereas the fetchStaticIps method only supports regions.
• Passing {{location}} into ReplaceVars doesn't invoke the fallback behaviour from getLocation, so even if it was useful & appropriate to use it would actually just construct an invalid name of project/my-project/:fetchStaticIps

Fixes #12928

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).
• 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).
• Generated Terraform providers, and ran make test and make lint in the generated providers to ensure it passes unit and linter tests.
• Ran relevant acceptance tests using my own Google Cloud project and credentials (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_datastream_static_ips`

Derived from GoogleCloudPlatform/magic-modules#7847

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.