Stop exporting systemserverclasspath_fragment when targeting S

Previously, when targeting the S release the generated sdk snapshot
would contain prebuilt_systemserverclasspath_fragment modules even
though they were only added in T.

This allows SdkMemberTypes to specify the set of target build releases
they support and ignores them when targeting an unsupported target
build release.

The Merged-In value was chosen to prevent this from being merged into
branches where it will conflict due to https://r.android.com/2105804.
That will allow this change to be submitted in tm-dev before it is
submitted in AOSP.

Test: m nothing
      packages/modules/common/build/mainline_modules_sdks.sh
      # Check that the for-S-build snapshots do not include SSCPFs.
Bug: 237718221
Change-Id: I2df08c2fcebf9b866695d691572a9d3783758b17
Merged-In: Ib6d1b72bc8399fbb39075494ae37da92f4b28d03