Properly handle JavaAdapterKt flow lifetimes.

Flows created through JavaAdapterKt#collectFlow must be explicitly
canceled when not used. This changelist ties the lifetime of a number of
such flows to the view attached state.

Fixes: 420871821
Flag: EXEMPT bugfix
Test: atest ComplicationHostViewControllerTest
Test: atest AmbientStatusBarViewControllerTest
Change-Id: Id7699a2b20edcec50aa8651e05c71366d7715774