Introduce a CustomIconCache for editing favorites

The cache will store custom icons for the current component and will
clear whenever the current component changes (as only the current
component can be edited).

Test: manual
Test: atest com.android.systemui.controls
Bug: 161440353
Change-Id: I8ac2e1ee983ad8ab714f050edaa8981a2307beca
Merged-In: I8ac2e1ee983ad8ab714f050edaa8981a2307beca
(cherry picked from commit 8f659543)