Improve lock annotation for InputMethodManager (2/N)

In CL[1], we added @GuardedBy("mH") annotation for some
fields which should be guarded by mH for lock annotation
improvement.

Annotate more fields we miss in CL[1].

[1]: I3b345da25841b328358d16695e3a29ee65ae8d83

Bug: b/236937383
Test: presubmit
Change-Id: Ibee725dff3ff3d52f5b4d58e8bf2d8837dba665e