fix: add cache invalidation on config change

[mellyeliu]

What changed / motivation ?

Let's invalidate the cache whenever StyleX config options change:

• Stringify config (without input/output paths, as accounted for) into key sorted JSON, hash output, add to cache check

Testing

Added test for config change

Pre-flight checklist

• I have read the contributing guidelines
  Contribution Guidelines
• Performed a self-review of my code

[github-actions]

workflow: benchmarks/size

Comparison of minified (terser) and compressed (brotli) size results, measured in bytes. Smaller is better.

@stylexjs/[email protected] size:compare
./size-compare.js /tmp/tmp.JMQqjhMLHe /tmp/tmp.8uT95Tn1pv

Results	Base	Patch	Ratio
stylex/lib/stylex.js
· compressed	729	729	1.00
· minified	2,541	2,541	1.00
stylex/lib/StyleXSheet.js
· compressed	1,266	1,266	1.00
· minified	3,776	3,776	1.00
rollup-example/.build/bundle.js
· compressed	567,110	567,110	1.00
· minified	10,232,512	10,232,512	1.00
rollup-example/.build/stylex.css
· compressed	100,626	100,626	1.00
· minified	757,176	757,176	1.00