Subscribe to activity recognition on charging only

This change makes the subscription of CHRE activity recognition depend
on device charging, which improves battery performance.

Test: atest DreamSuppressionStartableTest
Test: verified subscription only while charging
Fix: 445522597
Flag: com.android.systemui.dream_suppression
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:f219544ca37800e73c521cc6afae8ef635038679
Merged-In: Ib57802a4bb096ea199621fc95feaa046db6289e1
Change-Id: Ib57802a4bb096ea199621fc95feaa046db6289e1