Exclude non-observable insets change

When we notify insets changed, legacy behavior forces us to force
a new measure on the entire hierarchy. However, this can cause
jank in various scenarios.

Make sure that we don't report an insets change if non-observable
state changes.

Test: InsetsStateTest
Test: Swipe up to home while IME open
Bug: 157123435
Change-Id: I9c51066c6489888720b307240d03054cc18c4172