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 hashicorp/terraform-provider-google#12928

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`google_datastream_static_ips`

Derived from GoogleCloudPlatform/magic-modules#7847