add pipeline status monitor

[nicHoch]

Status logger and notification script for the pipeline.

SetUp via cron.
Query the number of open files still to process. Logs that number into a status file
and checks if the the number is constantly equal or increasing.

Sends an notification via mail if a possible pipeline stuck is detected.

[nicHoch]

@samaloney "unfortunately" we missed a stuck case on this weekend. i waited until i get the mail but forgot that i changed to another branch in me dev environment ...
but if you review it i can merge it into master soon

[samaloney]

If this is really a script maybe belongs in script folder rather than here?

[nicHoch]

all our entry-points / mains clis for regular use are in this processing folder. the script are more used as helpers on times ...

i will also add a entry point in the project setup

[codecov-commenter]

Codecov Report

Attention: 61 lines in your changes are missing coverage. Please review.

Comparison is base (a801e54) 77.79% compared to head (3b00fa6) 77.12%.

Files	Patch %	Lines
stixcore/processing/pipeline_monitor.py	0.00%	59 Missing ⚠️
stixcore/processing/pipeline_status.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #372      +/-   ##
==========================================
- Coverage   77.79%   77.12%   -0.68%     
==========================================
  Files          65       66       +1     
  Lines        6777     6836      +59     
==========================================
  Hits         5272     5272              
- Misses       1505     1564      +59     

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