Replace use of build-aml-prebuilts

The build-aml-prebuilts script is no longer necessary because:
- Support has been added in soong_ui for skipping just kati, but not
  config (previously it could only skip both together)
- A new product configuration that produces the same values that
  build-aml-prebuilts did for soong.variables has been created

These two together mean that we can ditch build-aml-prebuilts, which
should be easier to maintain since new required soong.variables don't
need to be added in multiple places.

Bug: 174315599
Test: art/build/build-art-module.sh (some diffs, but appear to work)
Change-Id: I4eae4153a62d50056e84a46f6d48ef8a811595ce
1 file changed