SAS 21 Compatibility

[clustercosmos]

epchain in assemble.py needs runradmonfix=N applying to both with and without oot events (the binary no longer comes with sas).

[DavidT3]

Fixing these identified problems should form part of a larger review of how backend changes are identified and brought to the attention of the developers. Each release of DAXA should be more specific about known-good supported SAS versions, and include warnings on initialisation if a newer/older version is detected. Sort of ties in to the problems @jessicapilling and @HallJoseph found in XGA, we could take a similar approach there.

For some backends (like CIAO) it is easier than others, because that is installable through conda we can just put it in the conda lock file (reminds me that issue #314 isn't complete yet).