Write an automated test of the PinnedLauncherApps user policy, using the AutoTest+Telemetry Enterprise Policy Test framework. This policy is a JSON list, and is dependent on whether or not the pinned app is installed. Test will use ExtensionSettings user policy to force-install certain test apps, though it will not thoroughly test the ExtensionSettings policy.

In general, the possible policy values are:
- NotSet: Default pinning is used at first. User can fully manage pinning of apps to the Shelf: Pin, Move, UnPin.
- [app_id1, app_id2, ...]: The listed apps, if installed for user, are pinned to the Shelf in the order listed.  If a default app is not listed (e.g., chrome, gmail), it will be unpinned from the Shelf.

Note: This test will not verify the UI behavior introduced in  issue 549083 : Pinned apps shadow user pinned apps. User can move/unpin user-added apps, but cannot pin new apps, or move/unpin policy-pinned apps. Those behaviors are thoroughly covered by unittests.