[chore][confmap] Do not merge: demonstrate empty slice handling

[evan-bradley]

Expands on #11755 to show how we could test for a 1:1 mapping between map[string]any <-> confmap.Conf <-> Config structs for []any(nil) and []any{} slices.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.59%. Comparing base (d0f5bda) to head (84e4ced).
Report is 36 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11882      +/-   ##
==========================================
+ Coverage   91.44%   91.59%   +0.14%     
==========================================
  Files         446      449       +3     
  Lines       23742    23761      +19     
==========================================
+ Hits        21712    21763      +51     
+ Misses       1654     1623      -31     
+ Partials      376      375       -1     

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