Rename API surface provided to mainline modules

This API surface is provided by platform and mainline modules to other
mainline modules. Rename it to module-lib API surface to align it with
the terminology in go/android-api-types

Test: go test ./bp2build
Test: go test ./cc
Change-Id: Ieb9f3214e66366fc2ceb6f47e2d6623acb537827