Refactor api.go to simplify Android.bp further

The gitlinter tool consumes the Android.bp file and from it mines
the module names of libraries that contribute to the public API surface.
The format required by the previous incarnation of api.go (creating a
list in Android.bp and passing that multiple times) did not lend itself
to being easily consumed by gitlinter.

So, change some of the constructs to simplify the Android.bp definition:
- hardcode a couple of "anomalies" inside the go code instead (which
  modules have only public APIs and what modules should be filtered
  from the lint DB). There's no real benefit to plumb them through the
  Android.bp.
- only pass the list of modules once (this allows inlining the list)

Also change the output filename of the genrules. This makes no practical
difference but does match the existing genrules.

Bug: 169103987
Test: in the followup-change that defines a combined_apis
Change-Id: I6715fa9d24603e3cbb8b09510b64c2bf6bac1f27