cc: Vendor modules should NOT derive its "SDK" level from VNDK

Although vendor modules can be built bundled, they are technially not
part of the "platform", as it cannot access platform libraries (system
partition) directly.
They can only link to a restricted set of platform libraries (LLNDK),
and access restricted set of APIs.
We used to derive the LLNDK API level from the VNDK version. However
after VNDK deprecation, there is no "VNDK version" anymore.
Instead we would just derive the value from platform SDK version:
* If building an in-development build, build vendor modules against the
  in-development "current" API level.
* If building a REL / Final build, vendor should target the latest
  stable API.

Bug: 320423828
Test: go test
Test: presubmit
Test: build and boot
Change-Id: I2c5ef6530e9046b2dcc282bc1f020d8a505eab15