configuration: env vars with array values rendered as a single string

[alessio-perugini]

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What kind of change does this PR introduce?

Fix a regression in passing multiple values to a single env var that wasn't correctly expanded.

What is the current behavior?

When passing multiple values in a single env var, they are rendered a single string, causing unexpected behaviors.

What is the new behavior?

Now we treat such values as multiple values and not as a single string. We split them by whitespace.

Does this PR introduce a breaking change, and is titled accordingly?

Other information

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.31%. Comparing base (3f0d43f) to head (651c32e).
Report is 3 commits behind head on master.

❗ Current head 651c32e differs from pull request most recent head 6e7613b

Please upload reports for the commit 6e7613b to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2644      +/-   ##
==========================================
+ Coverage   70.29%   70.31%   +0.02%     
==========================================
  Files         222      222              
  Lines       21308    21318      +10     
==========================================
+ Hits        14978    14990      +12     
+ Misses       5153     5151       -2     
  Partials     1177     1177              

Flag	Coverage Δ
unit	70.31% <100.00%> (+0.02%)	⬆️

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[alessio-perugini]

superseeded by #2645