fix(fullscreen magnification): Fix the race condition issues on the magnification border

(1) Create FullscreenMagnificationActivationState to manage actions
(2) Remove all Runnables that haven't been executed before removing the magnification border
(3) Perform modifications on the magnification border field on MainHandler only
(4) Clean up the resources when the tests end properly
(5) Create separate animators for show and hide border to avoid messing up the states and threading

Bug: 366388596
Bug: 365847277
Test: atest FullscreenMagnificationControllerTest
Flag: EXEMPT BUGFIX
Change-Id: I00d6d7448c72989ee1244c06a73451e65ee0fe4b