[Github Actions] Compress all bash shell setters into one default option per workflow

[valeriupredoi]

Description

This specifies the shell definition (bash, in this case) in a defaults section of the GA workflow, and more importantly, does this only once so that everytime a new command is added (via run key), one doesn't have to keep adding the bash definition above it; this makes the workflow a lot more readable; originally suggested by @bouweandela 🍺

Closes #2031

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[codecov]

Codecov Report

Merging #2126 (c7be416) into main (9d6b963) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2126   +/-   ##
=======================================
  Coverage   93.09%   93.09%           
=======================================
  Files         237      237           
  Lines       12794    12794           
=======================================
  Hits        11910    11910           
  Misses        884      884           

[valeriupredoi]

dis ready now @bouweandela

[bouweandela]

Looks much better than before!

[valeriupredoi]

many thanks for proposing and reviewing this, @bouweandela 🍺