Use WeaklyReferencedCallback annotation

Apply this annotation to several callback types to ensure write-only
member fields are kept during optimization, helping preserve lifecycle
semantics.

A follow-up change will clean up some of the @KeepForWeakReference
field annotations that should no longer be necessary.

Bug: 349245577
Test: FULL_SYSTEM_OPTIMIZE_JAVA=true m services
Flag: EXEMPT bugfix
Change-Id: Ied71a08d2b1a71b0e0789d863af6b61ae9b0918f