refactor: consolidated error/status code handling

[mccutchen]

Here we provide a standardized way to map errors to close codes, and take a naming pass through our errors and codes to better align them with the IANA's registry of WebSocket Close Codes.

[github-actions]

🔥 Run benchmarks comparing 67ec629 against main:

gh workflow run bench.yaml -f pr_number=40

Note: this comment will update with each new commit.

[codecov]

Codecov Report

Attention: Patch coverage is 95.55556% with 2 lines in your changes missing coverage. Please review.

Project coverage is 92.40%. Comparing base (0dbe072) to head (67ec629).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
websocket.go	93.75%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
- Coverage   92.65%   92.40%   -0.25%     
==========================================
  Files           3        3              
  Lines         449      461      +12     
==========================================
+ Hits          416      426      +10     
- Misses         26       28       +2     
  Partials        7        7              

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