CSCS-CI related issues

[aurianer]

• [x] #846
• [x] #930
• [x] #906
• [x] #925
• [x] #862
• [x] #962
• [x] #996
• [x] #1018
• [x] Check that all Jenkins configurations have been removed (#982 #1024 #1046)
• [x] #1037
• [x] #1025
• [ ] #894 (for now the spack cxx standard for this configuration is 17, the cxx standard for building is 20 and stdexec is disabled)
• [ ] #884
• [x] #1072
• [ ] #936
• [x] ~Potentially move the configurations to another platform than clariden once one is officially available for CI. Clariden is not intended for that but more for ML.~

Notes:

• the gcc9 cuda11 configuration is pinning fmt to version 9

[msimberg]

Perhaps worth opening issues for the following as well:

• GCC 10 + APEX configuration
• Release builds
• Performance CI (the one on Jenkins, not the one pushing to elastic)
• Moving daint builds to alps (daint mc to eiger, gpu to clariden) ?

[aurianer]

yes will do :)