Remove DistFiles from AndroidMk datastructures

The code that collects dists also supports getting them from
OutputFiles. Switch the few remaining usages of AndroidMk-based
disted files over to OutputFiles, and remove DistFiles from the
AndroidMk datastructures.

This should allow us to clean up more AndroidMk code in a followup
cl.

Bug: 398938465
Test: Confirmed that the ninja files for "m nothing dist" don't change after this cl.
Change-Id: I9eaed21018ef73ec36276556e7daa7201b272009