Retire Legacy Experiments and Systems

[dyokelson]

To Do List for retiring all legacy experiments and systems. Rewrites need to be complete and verified before we start deleting.

Task	Status	Comments/Issues/PRs
Rewrite all systems as system.py	In Progress	Still left: LUMI, Daint, Eiger, Juwels, Pascal, Grace, PR #454, #455
Rewrite all experiments as experiment.py	In Progress	Still left: Genesis, Salmon, Branson PR #460
Delete legacy dryruns	In Progress	some in PR #523
Rewrite systems table script for docs	Not Started	Issue #377
Rewrite experiments table script for docs	Not Started	Issue #377
Rewrite benchpark commands for new structure	Not Started	Issue #378
Delete legacy system definitions	Not Started	Move Grace to new way first
Delete legacy experiment ramble.yamls	Not Started	Move Grace to new way first
Delete legacy caliper modifier code	Not Started	Move Grace to new way first