[sb] new mobile icons

This replaces the old-new icons. The target size is 12sp height. This CL
also flags off the intrinsic size that SignalDrawable was doing. Since
that class is now a `DrawableWrapper`, it doesn't need to do this
overriding anymore and can defer to its wrapped icons.

Test: atest SystemUITests
Test: SystemIconsScreenshotTest
Flag: com.android.settingslib.flags.new_status_bar_icons
Bug: 391606042

Change-Id: I9bd732f12855d734c9d587252ef6e0cd0f8cb9e6