Make hue ::from_degrees and some palette::cast::* functions const fn

[Ogeon]

This makes the following functions const fn, as allowed by Rust 1.61.0:

• ::from_degrees for hue types
• palette::cast::into_array_ref
• palette::cast::from_array_ref
• palette::cast::into_uint_ref
• palette::cast::from_uint_ref

[codspeed-hq]

CodSpeed Performance Report

Merging #405 will degrade performances by 11.73%

_{Comparing const_fn (13368ac) with master (afa3b12)}

Summary

❌ 1 regressions
✅ 45 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	master	const_fn	Change
❌	matrix_inverse	438.9 ns	497.2 ns	-11.73%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.66%. Comparing base (afa3b12) to head (13368ac).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #405      +/-   ##
==========================================
- Coverage   82.66%   82.66%   -0.01%     
==========================================
  Files         127      127              
  Lines       19545    19539       -6     
  Branches    19545    19539       -6     
==========================================
- Hits        16157    16151       -6     
  Misses       3285     3285              
  Partials      103      103              

Components	Coverage Δ
palette	82.71% <100.00%> (-0.01%)	⬇️
palette_derive	81.98% <ø> (ø)