Change setup/assumptions s.th. multiple experiments can be started in parallel

[valentinaschueller]

It's not possible to start multiple experiments at once because they all generate a runscript and symlinks in the same place which might get overwritten by another experiment running simultaneously. For local runs, this is fine; but when I'm running on COSMOS/Tetralith it would be great to run multiple experiments in parallel without having to worry about this race condition.

[valentinaschueller]

This must have been an issue for other people using the AOSCM and maybe even in EC-Earth 3?

• check whether the ECE3-classic RTE scripts also explicitly create the runscripts/symlinks all in the same place instead of, e.g., in the run directory