site CI: report job status, check for exit codes, add machines and benchmarks

[slabasan]

Merge after #396. This PR extends CI support for site testing benchmarks. Closes #367.

• draft status to toggle running of gitlab
• reporting pass/fail status to github
• testing new workflow with saxpy on tioga
• kripke (gpu) on tioga
• add site user @alecbcs
• look at exit modifier in ramble

Save notes:
error message if try to init an experiment iwht a unsupported variant?
add grep here for available system+experiment variants (look for return code)
if grep CUDA; then
append CUDA to list of variants
iterate over list of variants
append cuda variant job to larger benchmark job
for loop over variants

[slabasan]

@pearce8 This one ready for merge

[alecbcs]

@slabasan it looks like this pipeline is running too many jobs / reserving too many nodes on Tioga. We've been asked to pause or halt until we can limit the number of jobs.

requested changes addressed

[slabasan]

@pearce8 Ready for merge