Add time taken to the completion message

[ubdbra001]

An attempt to resolve #1294

This records the datetime for each function in run_modules that later calls completion_message, and then passes it when completion_message is called to calculate the duration elapsed.

It doesn't break any tests but it would be good if someone else could test it on a real run.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.18%. Comparing base (98bc988) to head (812b0a6).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1374      +/-   ##
==========================================
+ Coverage   84.11%   84.18%   +0.06%     
==========================================
  Files          31       31              
  Lines        6448     6474      +26     
==========================================
+ Hits         5424     5450      +26     
  Misses       1024     1024              

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[SylviaWhittle]

@SylviaWhittle to check if this works in actual usage.

[SylviaWhittle]

Tested locally. Works. :)

Thank you.