[Extensions] Test that internal permissions are not allowed in manifests

Internal permissions are permissions that are used by the extensions
system, but should not be requested by developers in their extension
manifests. This functionality exists today, but appears to be
untested.

Add a new unittest to exercise it.

Bug: 1421424
Change-Id: I783bdac171c77bfc0efd89378ab874c7bc7031fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4321755


Auto-Submit: Devlin Cronin <rdevlin.cronin@chromium.org>
Reviewed-by: Tim <tjudkins@chromium.org>
Commit-Queue: Tim <tjudkins@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1115265}