Concentrate knowledge/handling of what Pub can/can't support in Pub itself

* Move throwing "Pub can't run on Windows" from PackageManagementAction to Pub, where another similar exception is already thrown.
* Also, fix an accidentally discovered bug in PackageServiceProperties.isSecondaryPackageResource().
Merge pull request #3816 from ussuri/pub-fixes

Concentrate knowledge/handling of what Pub can/can't support in Pub itself
Fix a few compile-time warnings
Merge pull request #3829 from ussuri/small-fixes-4

Fix a few compile-time warnings
Follow-up to #3765: fix #3815 "File filter and search view are broken"
Merge pull request #3830 from ussuri/consolidate-ui-in-topUi

Fix #3815 "File filter and search view are broken"
Remove no-longer-used concrete implementation of a method
Some renamings + final->const
Merge pull request #3831 from ussuri/minor-cleanups

Minor cleanups