Add slurm workers for calibration end-to-end test

[nefrathenrici]

This PR updates the calibration end-to-end test to use Distributed.jl and the updated ClimaCalibrate with task-based parallelism. The main two files changed are calibration/model_interface.jl and calibration/test/e2e_test.jl

ClimaCalibrate v0.0.6 has three changes relevant to this PR

• just requires forward_model instead of set_up_forward_model and run_forward_model
• addprocs(SlurmManager(n)) can be used to acquired Slurm workers
• Adds WorkerBackend to distribute forward_model runs across Julia workers

Other changes:

• Removed the Calibration test GHA, it does not have a clear purpose
• Removed the prior.toml and put it in the test script
• Added *.out to the gitignore because the worker output goes to .out log files.

[szy21]

I'm not sure if I'm the best person to review this. And I think Charlie is out? Maybe some other people who are more familiar with calibration can take a look?

[Sbozzolo]

Can you add some docs (inline comments would be fine) to give some context to those who read this file and are not familiar with ClusterManagers?

[Sbozzolo]

Is there documentation about the WorkerBacked?

[nefrathenrici]

Is there documentation about the WorkerBacked?

There is no documentation on the WorkerBackend at the moment, I am planning on updating the ClimaCalibrate as part of this PR but I can add some more information in this current PR as well.