Vendor apexes can be "updatable: true"

Vendor APEXes can be updatable unless it sets "use_vndk_as_stable:true".
When "updatable:true", it should meet the "updatable" requirements like
"should set min_sdk_version".

Bug: 274396342
Bug: 274041915
Test: m nothing (soong tests)
Change-Id: I746d8941c21e883c1eba3e1f1e5a414a67db071a