java_sdk_library: Use dist_stem when generating sdk snapshot file names

The API finalization process for platform releases copies various files
from the apistubs/ dist directory into prebuilts/sdk/<n>/...  Having
them use the same name in both places makes that process simpler. For
most modules the name of the file is derived from the name of the
module by appending a suffix but unfortunately, for some modules that
does not work. e.g. the conscrypt.txt file is produced by the
conscrypt.module.public.api module. The dist_stem property was added to
java_sdk_library to allow the stem name of the file to differ from the
module name.

The API finalization process for extension APIs does something similar
as it extracts various files from the snapshots and copies them into
the appropriate extension API specific directory in
prebuilts/sdk/extensions/<n>. Instead of copying files from the
apistubs/ dist directory (which is not built for trains) it copies them
from sdk snapshots that are built as part of the train.

Previously, the sdk snapshot used to derive the name of the files
within the snapshot from the name of the module, it ignored the
dist_stem property. This change causes it to use the dist_stem property
to make it consistent with the apistubs/ dist directory naming.

The file name is created in
sdkLibrarySdkMemberProperties.AddPropertyToSet() which does not have
access to the dist_stem property. So, it has to be supplied in the
sdkLibrarySdkMemberProperties instance in the new Stem property.

Bug: 248258460
Test: m nothing
      BUILD_NUMBER=fixed packages/modules/common/build/mainline_modules_sdks.sh --build-release=latest
      # Ran the previous command before and after and make sure that the
      # conscrypt, art and icu sdk snapshots use the dist_stem value but
      # none of the other snapshots are affected.
Change-Id: Ied52003de63dcdb86a252a39bb8781f85d51a6ff