fix: Trim white space from string slice retrieved from environment

[jannfis]

See #10270 (comment)

Also, while at this module, I took a shot at the unit tests for util/env, homogenizing them and add tests for StringFromEnv() and StringsFromEnv() functions.

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[codecov]

Codecov Report

Merging #10275 (c98f40c) into master (5515cde) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #10275      +/-   ##
==========================================
+ Coverage   46.10%   46.13%   +0.03%     
==========================================
  Files         228      228              
  Lines       27958    27960       +2     
==========================================
+ Hits        12889    12900      +11     
+ Misses      13322    13314       -8     
+ Partials     1747     1746       -1     

Impacted Files	Coverage Δ
util/env/env.go	100.00% <100.00%> (+13.04%)	⬆️

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[notfromstatefarm]

LGTM!

[crenshaw-dev]

lgtm!