Migrate from InsetsInfo.contentInsets to WindowManager.LayoutParams#providedInternalInsets

- This allows us to distinguish taskbar's ITYPE_EXTRA_NAVIGATION_BAR insets from its ITYPE_BOTTOM_TAPPABLE_ELEMENT insets
- Set nav bar insets as before (contentInsets)
- Set tappable elements insets the same, except when taskbar is stashed, in which case set to 0

Test: TaplTestsTaskbar; manually stash/unstash taskbar, open IME, open Calculator (which uses tappableElement() insets) and Contacts (which uses systemBars())
Fixes: 215411414
Change-Id: If00f7a590b0780715d5b8159f5135054364ce84e