Feat: subfile overrides

[adamSherwoodGenieAI]

closes #2938

• adds an overrides optional parameter to Compiler.compile and the Packer methods
• adds tests for the overrides parameter
• updates Packer usage docs
  • adds usage example for Packer.toString and Packer.toStream which were undocumented
  • adds brief explanation for the optional prettify parameter which was undocumented
  • adds usage example for overrides parameter

Let me know if this needs anything else

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (eb2174e) to head (e53209f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2941   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          286       286           
  Lines         8363      8390   +27     
  Branches      1409      1410    +1     
=========================================
+ Hits          8363      8390   +27     

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[adamSherwoodGenieAI]

@dolanmiu This is the PR related to that conversation we had in #2938

[dolanmiu]

Looks good, merged