Convert api.xml dist rules to Soong

...from make to support dist'ing *-api.xml files in soong-only builds.

Test: m droid dist --soong-only && ls out/dist/api.xml
Bug: 395162087
Bug: 394365683
Change-Id: I98e92423a107d24b04e6f6f0f96c23c24de01fa5