Main log export defaults

[umairidris]

While reviewing the main log exports module I noticed a few improvements could be made there too for defaults.

• unique_writer_identity should be true.
  https://cloud.google.com/logging/docs/api/tasks/exporting-logs
  When exporting logs, Logging adopts this identity for authorization. For increased security, new sinks get their own unique service account:

• include_children should be true, since most audit users probably want resources witin folder and orgs to be captured by default.

We can probably wait till v6 (whenever that is) to make the improvements.

[github-actions]

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