AthenaPoolCnvSvc: Default to using ZSTD instead of ZLIB for temporary files in the CA-based configuration

For all upstream data products we use LZMA w/ a compression level of 1. For temporary files, we used to switch to ZLIB to speed things up a bit. This MR updates the latter to ZSTD, which is a bit more performant than ZLIB both in terms of speed and disk-space.

cc: @gemmeren @tadej