Reland "Fix spacing and header protection for All Apps" after QPR1 merge

* Ensure that the expected header height is recalculated before/after
  search or orientation change. Otherwise, personal/work tabs will have
  different spacing behavior after these things occur; they will stick
  to the very edge of the search bar when scrolling down, with little
  to no spacing in between.
* Stabilize personal/work tabs when scrolling down. To do this, we do
  not add padding for floating header rows when we have no such rows.
* Various spacing adjustments in res/values/dimens.xml.

Test: Manual: Check consistent behavior of spacing and drawn header
rectangles in different conditions that are affected by this change:
1. Apps: Many installed (scrollable), and few (not scrollable).
2. Work profile: With and without one.
3. Search results.
4. Font size settings, smaller and larger.
5. (No known impact) Display size settings, smaller and larger.
6. Home screen rotation enabled, in landscape and portrait.

Issue: calyxos#1260
Original-Change-Id: I5cbf47eb4a734e9ce9b42d8ef9a27a167d614da0
Change-Id: I586f73325cecefcbed3a67f311710d1c8abffb85