lib.io: Implement *Port from RFC 55.

[wanda-phi]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 98.26087% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 89.50%. Comparing base (7445760) to head (186d0bf).

Files	Patch %	Lines
amaranth/build/res.py	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1214      +/-   ##
==========================================
+ Coverage   89.39%   89.50%   +0.11%     
==========================================
  Files          43       43              
  Lines        9516     9616     +100     
  Branches     2283     2314      +31     
==========================================
+ Hits         8507     8607     +100     
+ Misses        820      819       -1     
- Partials      189      190       +1     

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