Send Power Key Ups and Stem Primary KeyEvents to Status Bar

This allows Status Bar to listen and react to Power Key up events and
Stem Primary Key events. Coupled with its current callback hooks for
Power Key down, and its ability to dynamically modify these keys'
behaviors, this change allows Status Bar to give these keys custom
user-visible behaviors for specific usecases. For example, in Wear OS,
touch lock naturally calls for a non-touch mechanism to exit the touch
lock mode, and Wear OS uses special patterns of these keys to both
educate the user on how to exit the mode, as well as to let the user
exit the mode. Wear OS can now, in its System UI, dynamically modify
these keys' behavior in addition to reacting to their up/down events to
achieve this. A demo of this behavior is prototyped at
http://shortn/_5gMuu4pXBm.

Bug: 283029769
Test: manual, and see demo
Change-Id: I062473cb9209da202dea2c0eed3c576dc9826b27