feat(param): parse embedded struct

[Fazt01]

Param package can parse into embedded structs. Inspired by json package, where the package CAN set unexported embedded struct (only if non-pointer or non-nil-pointer), as long as it's fields are exported.

Also removed some useless customization to simplify the package (separate commit)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.04%. Comparing base (f9d8e66) to head (e4a1b2e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
+ Coverage   64.08%   67.04%   +2.95%     
==========================================
  Files          12       12              
  Lines         646      704      +58     
==========================================
+ Hits          414      472      +58     
  Misses        221      221              
  Partials       11       11              

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