[componenttest] Improve config struct checks

[evan-bradley]

Description

Improves our config struct checks by allowing for a few more cases that are possible with mapstructure.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.19%. Comparing base (7d3e03e) to head (d67b8bb).
Report is 27 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12590      +/-   ##
==========================================
+ Coverage   92.18%   92.19%   +0.01%     
==========================================
  Files         469      469              
  Lines       25394    25395       +1     
==========================================
+ Hits        23409    23413       +4     
+ Misses       1574     1572       -2     
+ Partials      411      410       -1     

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