m3: impl basic Material3 design AlertDialog

This is the first drop of Material3 AlertDialog styling. It requires further
refines on the padding and sizing(tracked by b/372623420).

Flag: EXEMPT. xml change
Test: PlatformMaterialUiTestApp's Dialog Demo
Bug: 372584107
Change-Id: I4c0f5189917a45896e8a19574e9705385daa5ff2