chore(ci): Change should-notify-slack to disable-slack-notification and extract scripts from the workflow definition

[luislhl]

Acceptance Criteria

• We should extract the python CI logic from inside .github/workflows/docker.yml to an actual .py file
• We should have unit tests for the extracted CI logic
• Change the variable should-notify-slack to disable-slack-notification, to make the code clearer

Note: I moved the logic to extras/github/docker.py alongside its test file, but if there is a better place just let me know.

[codecov]

Codecov Report

Merging #548 (3a33c24) into dev (3a33c24) will not change coverage.
The diff coverage is n/a.

❗ Current head 3a33c24 differs from pull request most recent head d2f2252. Consider uploading reports for the commit d2f2252 to get more accurate results

@@           Coverage Diff           @@
##              dev     #548   +/-   ##
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  Coverage   83.31%   83.31%           
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  Files         212      212           
  Lines       18729    18729           
  Branches     2596     2596           
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  Hits        15604    15604           
  Misses       2561     2561           
  Partials      564      564           

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