feat: coordinate transformation functions with momentum names

[Saransh-cpp]

Description

Fixes #168

• add tests

Checklist

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[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (4cec27d) 82.70% compared to head (11a13fc) 82.87%.

Files	Patch %	Lines
src/vector/_methods.py	75.00%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #424      +/-   ##
==========================================
+ Coverage   82.70%   82.87%   +0.17%     
==========================================
  Files          96       96              
  Lines       11453    11533      +80     
==========================================
+ Hits         9472     9558      +86     
+ Misses       1981     1975       -6     

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[jpivarski]

Looks good to me! The problem with momentum names is that the temporal coordinate names are very overloaded: E, e, energy and M, m, mass. (I don't think we should have all combinations; there are a lot of combinations!)

If someone's using this in an environment that has tab-complete, that should help a lot. That's why it's good that the alias you chose is the fully spelled-out word: the lower-case single-letter will expand to that, at least.