fix(gatsby): Update mini-css-extract-plugin to fix inc builds issue

[LekoArts]

Description

Update mini-css-extract-plugin to fix a weird cache/recompilation issue. css-loader also needed to be updated due to webpack-contrib/css-loader#1384 bug (hash was different in client-side/SSR)

Failing test assertion was added in #33982 and this PR should fix this.

Related Issues

Fixes #33450

[ch40612]

[LekoArts]

The tests for global styles are failing now because the url() usage has been changed. In https://github.com/webpack-contrib/css-loader/releases/tag/v6.0.0 it says

file-loader and url-loader are deprecated, please migrate on asset modules, since v6 css-loader is generating new URL(...) syntax, it enables by default built-in assets modules, i.e. type: 'asset' for all url()

So in the e2e test the generated HTML is pointing to a different location than what is generated. Right now both at public and public/static font files are generated.

We'd need to further look into https://webpack.js.org/guides/asset-modules/