Avoid IconView's setModalAlpha interfere with setContentAlpha

- Because ag/27301532 we have restriction in setModalness that forbid setModalAlpha be called multiple times, this was a hack to avoid setModalAlpha interferring with setContentAlpha
- As part of ag/27301532 modalness.set no longer have the field != value check, which cause the regression that icon appears in quick switch carousel
- Now it follows IconAppChipView's implementation to use MuiliValueAlpha

Bug: 339787593
Test: Swipe up from app, or quick switch then swipe up, icon shouldn't be visible
Flag: EXEMPT refactor
Change-Id: I0abb8df951ef32ba8a0f9bbfa385c0aa3b96dd7f