Quickly fail if an existing job has the same ID

[nweires]

Fail quickly if the user tries to start a job with the same ID as an existing job.

We still have the option to reattach to an existing job later, but for now we should at least fail early instead of after the Docker image has been built and pushed.

[github-actions]

File	Coverage
All files	86%	✅
base.py	90%	✅
eagle.py	77%	✅
exc.py	57%	✅
local.py	70%	✅
postprocessing.py	83%	✅
utils.py	91%	✅
cloud/docker_base.py	87%	✅
sampler/base.py	79%	✅
sampler/downselect.py	33%	✅
sampler/precomputed.py	93%	✅
sampler/residential_quota.py	61%	✅
test/test_docker.py	33%	✅
test/test_validation.py	97%	✅
workflow_generator/base.py	90%	✅
workflow_generator/commercial.py	53%	✅
workflow_generator/residential_hpxml.py	86%	✅

Minimum allowed coverage is 33%

Generated by 🐒 cobertura-action against b08b32f

[nweires]

I updated this quite a bit, so please take another look.

[lathanh]

Quickly fail if...

FYI, "fail-fast" is a fairly well-defined term for this.