Moves the generated Android.bp file from the root of the snapshot zip
file into the sdk_library/ sub-directory to allow the zip to be
unpacked in a directory that already contains an Android.bp file that
defines the apex_set for the corresponding APEX.
Also, removes the stubs_src property from the generated Android.bp
file.
Bug: 218685706
Test: packages/modules/common/build/mainline_modules_sdks.sh --build-release=R
atest --host mainline_modules_sdks_test
# deleted vendor/unbundled_google/modules/IpSecGooglePrebuilt from rvc-dev checkout.
# unpacked out/soong/mainline-sdks/for-R-build/ipsec-module-sdk-current.zip
# ran "m nothing"
Change-Id: I03e2060dc06338a8d0102744f79c75d33d567a17
fa90e1e5e0