DO NOT MERGE Use KeyguardStateController for #isShowing

Remove calls that route through
StatusBarKeyguardViewManager/KeyguardViewController. This
was unnecessary and led to confusion. Instead, all components should
directly check KeyguardStateController for #isShowing and #isOccluded.

For now, this CL retains the keyguardVisibility callback in
KeyguardUpdateMonitor, where keyguardVisibility is defined as when
KeyguardStateController, our source of truth).

Test: builds
Test: atest SystemUITests
Bug: 248089638
Fixes: 251880943
Change-Id: I7c6373d2fa81ab2063234aae338b1b9643038e6a