Add Logging Sink data source.

[modular-magician]

New data source google_logging_sink added. It allows retrieving information about a Log Sink. The main use case to get Log Sink writer identity to grant it with permissions on the destination or to put the identity into VPCSC access level (for org, folder or billing account sinks).

Internal reference: b/268081935
Related external issue: hashicorp/terraform-provider-google#12083

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`google_logging_sink`

Derived from GoogleCloudPlatform/magic-modules#7250