feat: make saturation generic over the number type

[kayagokalp]

This makes the entire pipeline generic over the saturation number type, which enables easy experimentation with fractional and floats during the saturation. There are some limitations around egg, specifically define_language! macro which prevents me from making the language itself generic as well.

[codecov]

Codecov Report

Attention: Patch coverage is 67.94521% with 117 lines in your changes missing coverage. Please review.

Project coverage is 53.27%. Comparing base (672f79f) to head (f6572f5).

Files	Patch %	Lines
fluido-generation/src/lib.rs	0.00%	87 Missing ⚠️
fluido-core/src/lib.rs	0.00%	13 Missing ⚠️
fluido-types/src/number.rs	93.44%	8 Missing ⚠️
e2e-tests/src/harness.rs	0.00%	4 Missing ⚠️
fluido-parse/src/parser.rs	88.23%	2 Missing ⚠️
fluido-ir/src/graph.rs	91.66%	1 Missing ⚠️
fluido-types/src/fluid.rs	98.24%	1 Missing ⚠️
fluido/src/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
+ Coverage   49.27%   53.27%   +3.99%     
==========================================
  Files          20       20              
  Lines        1656     1819     +163     
==========================================
+ Hits          816      969     +153     
- Misses        840      850      +10     

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