Stylelint 15 deprecates a heap of rules which will be removed in 16.
We can't use 16 because it's ESM and requires a big restructure of our
build process.
We can temporarily silence the deprecations and then when we update our
build tooling we can make use of @stylistic/stylelint-plugin to add the
rules back.
This commit:
- bumps stylelint and related dependencies accordingly
- fixes issues identified with newer sniffs
- temporarily silences deprecation warnings
Remove the csslint config, remove an invalid property.
Kept csslint ignore lines becacase stylelint seems to respect them and
more work will be happening on css cleanup in MDL-55372.
