Consolidate the behavior and style of side stage outline

Update the style of side stage outline to match the current design. And
make sure the outline will interact properly with task bar expanding,
collapsing, swipe up, drag to split, recents shortcut to split and drag
divider bar to resize gestures.

Bug: 200850654
Test: atest WMShellUnitTests
Test: enable side stage outline, observed it behaves properly.
Change-Id: I3f0795adc34a0efb19d35b78d54364da4189a043