MGARD, with MDR feature built and used in one CI image

[pnorbert]

Do we have any MGARD testing already? Then we can just update the version requirement (1.5.2) and build it with MDR on. Otherwise, we need to create a build script for the first time for MGARD.

[scottwittenburg]

Our ubuntu images that use spack to install adios2 dependencies use mgard@2023-01-10. But looking at the spack mgard package, it seems to come from a fork which is maintained specifically to support the spack package. And the spack package does not yet have a version corresponding to the 1.5.2 release of the upstream mgard, though it does seem to be available in the fork (see this commit).

So some options are:

1. update the spack package to make 1.5.2 of mgard available in spack, then wait until that change appears in an E4S release, so we can use it in our ubuntu ci image
2. add version 1.5.2 of mgard to some other image and test with that immediately

For option 1, it would be good to get feedback from @robertu94 as to whether it makes sense to point to the commit linked above from the spack package, and whether that version should be preferred. For option 2, we can just proceed, and then we'll be testing against two different versions of mgard in our CI, which could have both pros and cons.

Also maybe there's some other option(s) I'm forgetting, and maybe @vicentebolea will have some thoughts.

[robertu94]

If you open a PR to add 1.5.2, I'll merge it.

[scottwittenburg]

Thanks @robertu94 I've made a draft PR, but added some questions since I'm not sure exactly what's needed/required.