JP-2980 Documentation improvement for multiprocessing: a script which spawns processes on import will cause system failure

[penaguerrero]

Resolves JP-2980

Closes #7308

This PR addresses needed documentation requested in several help desk tickets. This is connected to GitHub issues:
#8404
#8306

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.76%. Comparing base (2fb073e) to head (1baa4c8).
Report is 36 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8408      +/-   ##
==========================================
+ Coverage   75.31%   75.76%   +0.45%     
==========================================
  Files         474      476       +2     
  Lines       38965    39404     +439     
==========================================
+ Hits        29345    29854     +509     
+ Misses       9620     9550      -70     

Flag	Coverage Δ		*Carryforward flag
nightly	77.64% <ø> (+0.31%)	⬆️	Carriedforward from ccfa560

*This pull request uses carry forward flags. Click here to find out more.

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[hbushouse]

Just checked the docs built from the CI test in this PR and they look good.

[hbushouse]

@penaguerrero Does this also close #8404 or is it just related?

[penaguerrero]

it is not related. In a conversation with Brett we discussed that a cause for the memory issue could be the multiple re-openings of datamodels. He is looking into that separately.