Cache isStylusHandwritingAvailable for user

InputMethodManager's isStylusHandwritingAvialable is called frequently
from all toolkits before initiation. Caching this value on client app
should help reduce the hover icon and initiation latency

Refer to doc in bug for approach

Bug: 288618291
Bug: 287109569

Test: atest StylusHandwritingTest
Test: atest MultiUserTest
Change-Id: I6d89d82589e4946e07bfbc4b97811fe4537b1a9b