Minor optimizations and cleanup code.

[TimothyMakkison]

• Remove unneeded usings
• Remove some null checks (it looks like nullable annotations were hastily added so I kept most of the redundant checks in place)
• Fixed typos
• Inverted ifs and used early returns/continutes to reduce nesting
• Removed unneeded parameterTypes.ToArray() call
• Replaced dict.ContainsKey -> dict[key] with TryGetValue where appropiate

[TimothyMakkison]

Converted to draft until I fix the whitespace

[codecov]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (bca7448) 85.40% compared to head (d583996) 85.46%.

❗ Current head d583996 differs from pull request most recent head e013bfc. Consider uploading reports for the commit e013bfc to get more accurate results

Files	Patch %	Lines
Refit/RequestBuilderImplementation.cs	85.00%	3 Missing and 3 partials ⚠️
Refit/FormValueMultimap.cs	89.65%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1596      +/-   ##
==========================================
+ Coverage   85.40%   85.46%   +0.06%     
==========================================
  Files          33       33              
  Lines        1685     1686       +1     
  Branches      295      294       -1     
==========================================
+ Hits         1439     1441       +2     
+ Misses        167      166       -1     
  Partials       79       79              

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[TimothyMakkison]

Closing because I've split this pr into #1617 and #1619

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.