1) When it is not set in base apex, default file name should be set explicitly in bp2build converter of apex
2) The manifest file path should be used as-is when base apex and override_apex is in the same Android.bp
3) The manifest file path should be prepended with package of base apex when base apex and override_apex is in different Android.bp
Bug: 216442475
Test: m nothing
Change-Id: Icd3523ebc31d885f67bea02aec05dbfc77671e87