Remove UserLifecycleListener deps from SecureSettingsWrapper

As part of removing the dependency on UserLifecycleListener from
random utility classes under com.android.server.inputmethod.*, this CL
updates SecureSettingsWrapper so that it does not need to register
UserLifecycleListener by itself.

This is a mechanical refactoring CL. The observable semantics should
remain unchanged.

Bug: 352354308
Test: atest FrameworksInputMethodSystemServerTests
Flag: EXEMPT refactor
Change-Id: If903fe15e7e71eed2fccb45c082d8efb8176f26c