ApplicationClusterEntryPoints should explicitly close PackagedProgram

FLINK-21164 introduced PackagedProgram#close to clean up temporary jars, and with FLINK-9844 the contained classloader will also be closed beforehand. This allows these files to be cleaned up properly.

To make it obvious that this also happens in the application cluster entrypoints (and to reduce the chances of this potentially leaking code being copied elsewhere) we should adjust the entrypoints to explicitly close the PackagedProgram.