Enable Floating Search by default and update tests accordingly.

Tests need to be updated to account for the new placement of the
searchbar because it overlapped with touch events for scrolling:
 - Scroll back to top: Instead of scrolling from the top of the
   container which could overlap status bar in landscape, scroll
   from the bottom of the top-most visible app icon.
 - Scroll down: swipe up from bottom padding to top of top-most
   visible icon.
 - Close all apps: swipe down fom top of recyclerview instead
   of search bar.

For Launcher3, the floating flag is not fully supported yet, so
there were some layout issues which are now resolved by ignoring
the flag if the searchbar is still at the top.

Fix: 261873937
Test: Ran tests, manual
Change-Id: I7d6fc7deac630835b96fc173211ce31271152607