Add From implementations for changing Rgb component types between u8, f32 and f64

[Ogeon]

This adds From implementations for Rgb and Rgba for changing the component type between u8, f32 and f64. This should hopefully be easier to discover and remember than from_format and into_format.

[codspeed-hq]

CodSpeed Performance Report

Merging #390 will degrade performances by 10.25%

_{Comparing rgb_component_type_from_impls (04dbb1a) with master (a22067b)}

Summary

⚡ 1 improvements
❌ 1 (👁 1) regressions
✅ 44 untouched benchmarks

Benchmarks breakdown

	Benchmark	master	rgb_component_type_from_impls	Change
👁	matrix_inverse	243.3 ns	271.1 ns	-10.25%
⚡	multiply_3x3	455.6 ns	400 ns	+13.89%

[codecov]

Codecov Report

Attention: Patch coverage is 19.51220% with 33 lines in your changes are missing coverage. Please review.

Project coverage is 83.35%. Comparing base (a22067b) to head (04dbb1a).

Files	Patch %	Lines
palette/src/rgb/rgb.rs	19.51%	33 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #390      +/-   ##
==========================================
- Coverage   83.48%   83.35%   -0.14%     
==========================================
  Files         125      125              
  Lines       20145    20184      +39     
  Branches    20145    20184      +39     
==========================================
+ Hits        16818    16824       +6     
- Misses       3170     3203      +33     
  Partials      157      157              

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