Consolidate baseContext, BaseContext, and BaseModuleContext

blueprint.BaseModuleContext is the set of methods available to all
module-specific calls (GenerateBuildActions or mutators).  The
android package split the same functionality across baseContext (nee
androidBaseContext), BaseModuleContext, and BaseContext.
Consolidate all of them into android.BaseModuleContext.

Test: m checkbuild
Change-Id: I2d7f5c56fd4424032cb93edff6dc730ff33e4f1e