Export EXIT_CODE from the user provided command, and propagate the error to Cloud Console UI

[Obliviour]

• Refactor command argument passthrough
• Spelling
• Enable EXIT_CODE to be of the user provided command
• Move appending to command / internal command to its own function
• Remove outdated arguments from workload create
• Propagate error message to cloud consule

Fixes / Features

• EXIT_CODE to be linked to the user provided function

Testing / Documentation

Is Happy workload successful with EXIT_CODE=0

python3 xpk.py workload create --cluster vbarr-v4-xpk-test-tpu --workload vbarr-xpk-error-test-2 --command "bash test.sh" --tpu-type=v4-8 --num-slices=1 --zone=us-central2-b --project=cloud-tpu-multipod-dev

Error workload with EXITO_CODE=1

python3 xpk.py workload create --cluster vbarr-v4-xpk-test-tpu --workload vbarr-xpk-error-test-fail --command "bash test.sh && ech a" --tpu-type=v4-8 --num-slices=1 --zone=us-central2-b --project=cloud-tpu-multipod-dev

Debug flag work?

XLA Flag work?

python3 xpk.py workload create --cluster vbarr-v4-xpk-test-tpu --workload vbarr-xpk-error-test-fail --command "bash test.sh && ech a" --debug-dump-gcs=some_bucket --enable-debug-logs --tpu-type=v4-8 --num-slices=1 --zone=us-central2-b --project=cloud-tpu-multipod-dev

Does the error propagate to pantheon UI?

• [ y] Tests pass
• [ y ] Appropriate changes to documentation are included in the PR