Add elevation to the autoclick panel

Add a level 4 elelvation on hover and level 3 elevation on resting.

Screenshot:
go/sc-njixmty5mti1mdq1mdqzmnxjytq3nzvjyy1mma

Bug: 413445844
Test: manually verified on test devices
Flag: com.android.server.accessibility.enable_autoclick_indicator
Change-Id: I20a343236be74185e76e5d61e25c5f661f341902