perf: implement fastpath for removing CSSRules (#7112)
perf: implement fastpath for removing CSSRules (#7112)

- Check if we can use `replaceSync` to have a performant way to remove all the CSSRules from the sheet.
- Remove ~70-200ms from `prepareOverridesSheet` function.
darkreader/darkreader,darkreader/darkreader,darkreader/darkreader,alexanderby/darkreader,alexanderby/darkreader,alexanderby/darkreader