Implement equality operator synthesization

[kyouko-taiga]

Everything is in the title. No more tedious fun infix==(_ other: Self) -> Bool.

[codecov]

Codecov Report

Attention: Patch coverage is 97.02970% with 6 lines in your changes missing coverage. Please review.

Project coverage is 87.83%. Comparing base (b5bd439) to head (3742593).
Report is 12 commits behind head on main.

Files	Patch %	Lines
Sources/IR/Emitter.swift	96.87%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1563      +/-   ##
==========================================
+ Coverage   87.77%   87.83%   +0.05%     
==========================================
  Files         372      372              
  Lines       22491    22568      +77     
==========================================
+ Hits        19741    19822      +81     
+ Misses       2750     2746       -4     

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