Delete esbuild and webpack plugins

[necolas]

What changed / motivation ?

Removes the remaining deprecated plugins - esbuild-plugin and webpack-plugin.

[github-actions]

workflow: benchmarks/size

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

[email protected] size:compare
node size/compare.js /tmp/tmp.0ELHKt4xwp /tmp/tmp.ztjlFfCqmQ

Results	Base	Patch	Ratio
stylex/lib/stylex.js
· compressed	985	985	1.00
· minified	3,154	3,154	1.00
stylex/lib/StyleXSheet.js
· compressed	1,266	1,266	1.00
· minified	3,776	3,776	1.00
benchmarks/size/.build/bundle.js
· compressed	537,611	537,611	1.00
· minified	7,435,904	7,435,904	1.00
benchmarks/size/.build/stylex.css
· compressed	100,609	100,609	1.00
· minified	755,721	755,721	1.00

[mellyeliu]

looks like there's still some references to esbuild and webpack-plugin in packages/docs/docs/learn
/07-ecosystem.mdx packages/docs/docs/learn/03-installation.mdx let's remove before landing

[mellyeliu]

LGTM otherwise!

[necolas]

Thanks, removed the content you pointed out.