Rule based number formatting

[blagasz]

Number spelling based on the pure Python implementation of the CLDR RBNF engine.

Currently only supports whole numbers (cardinal, ordinal, year) as fractional numbers are not well-defined and not universally implemented in CLDR.

Based on the original PR #660 with useful enhancements from @akx at #682 and additional work from the original author:

• extensive test cases are generated
• dataclass added to make parsing context more readable in code
• linting and debugging including the removal of recursion errors

Extensive test cases are added, but should be considered smoke tests until a native speaker reviews them for each language.

Based on an earlier discussion: https://github.com/python-babel/babel/pull/114 and referenced in https://github.com/python-babel/babel/issues/179

Supersedes #682

[codecov[bot]]

Codecov Report

:x: Patch coverage is 97.88732% with 6 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 92.27%. Comparing base (50635d8) to head (bb56a15).

Files with missing lines	Patch %	Lines
babel/rbnf.py	97.83%	6 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1232      +/-   ##
==========================================
+ Coverage   91.93%   92.27%   +0.33%     
==========================================
  Files          27       28       +1     
  Lines        4688     4972     +284     
==========================================
+ Hits         4310     4588     +278     
- Misses        378      384       +6     

Flag	Coverage Δ
macos-14-3.10	91.15% <94.01%> (+0.17%)	:arrow_up:
macos-14-3.11	91.31% <97.88%> (+0.39%)	:arrow_up:
macos-14-3.12	91.51% <97.88%> (+0.38%)	:arrow_up:
macos-14-3.13	91.51% <97.88%> (+0.38%)	:arrow_up:
macos-14-3.8	91.02% <94.01%> (+0.18%)	:arrow_up:
macos-14-3.9	91.08% <94.01%> (+0.17%)	:arrow_up:
macos-14-pypy3.10	91.15% <94.01%> (+0.17%)	:arrow_up:
ubuntu-24.04-3.10	91.17% <94.01%> (+0.17%)	:arrow_up:
ubuntu-24.04-3.11	91.33% <97.88%> (+0.39%)	:arrow_up:
ubuntu-24.04-3.12	91.53% <97.88%> (+0.38%)	:arrow_up:
ubuntu-24.04-3.13	91.53% <97.88%> (+0.38%)	:arrow_up:
ubuntu-24.04-3.8	91.04% <94.01%> (+0.18%)	:arrow_up:
ubuntu-24.04-3.9	91.10% <94.01%> (+0.17%)	:arrow_up:
ubuntu-24.04-pypy3.10	91.17% <94.01%> (+0.17%)	:arrow_up:
windows-2022-3.10	91.16% <94.01%> (+0.17%)	:arrow_up:
windows-2022-3.11	91.32% <97.88%> (+0.39%)	:arrow_up:
windows-2022-3.12	91.52% <97.88%> (+0.38%)	:arrow_up:
windows-2022-3.13	91.52% <97.88%> (+0.38%)	:arrow_up:
windows-2022-3.8	91.13% <94.01%> (+0.17%)	:arrow_up:
windows-2022-3.9	91.09% <94.01%> (+0.17%)	:arrow_up:
windows-2022-pypy3.10	91.16% <94.01%> (+0.17%)	:arrow_up:

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