Added optional custom script post processing task

[asall]

Description

Added optional custom script post processing task in run_queued_resource_test()

• Optional bash script which will be run after run_model() task as part of the
  post_proces task group.
• custom script will run regardless of the result from run_model() allowing it to do
  get metrics, logs, etc from failed test runs.

Tests

Tested existing DAGs that use the run_queued_resource_test() function

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run one-shot tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed.