Set min_sdk_version for updatable mainline modules

Modules contributing mainline modules (APK/APEX) should set
min_sdk_version as well as apex_available.

For now setting min_sdk_version doesn't change build outputs.
But build-time checks will be added soon.

Bug: 145796956
Bug: 150999716
Test: m
Change-Id: Ifaecb49a47a1f43edea3ea06e1cf704a177d1044