Fix implict bp broken ui.

This CL fixes `isIconViewLoaded` logic by:
1. Check `modalities` to decide whether an icon should show.
2. If an icon should show, in `PromptIconViewBinder`, check `size` to
   update `_isIconViewLoaded` values. With this, when implicit face
   fails, size changes, `_isIconViewLoaded` could be updated to true.

Flag: N/A
Bug: 328677869
Bug: 328656309
Test: atest PromptViewModelTest
Change-Id: I04eb34ba3e2e118e4b4b9f5c8c023945880c38ff