Remove DefaultImeVisibilityApplier

With the changes in [1] and [2], there is no actual need anymore to have
a separate DefaultImeVisibilityApplier class. Thus, moving the remaining
methods (show/hide screenshot, perform show/hide) to IMMS.

[1]: I8e3a74ee579f085cb582040fdba725e7a63d6b85
[2]: I1399ec6c9e3f5ed70f02ba2326edd0c73eb930b4

Bug: 433457669
Test: atest com.android.server.inputmethod
Flag: EXEMPT refactor
Change-Id: Id02bfb3f44d57200422b6eb1e5e678f1abf751c3