Support sitekey option for content filters in MV3

Background

In MV2 "sitekey" option is supported for both content filters and URL filters. In MV3 we still using our FilterEngine from MV2 for content filters and for element hiding.

We need to make it working in MV3 context the way it worked in MV2.

We've also done some research about sitekeys in MV3.

TODO

Make sure:

1. it works in MV3 service worker
2. we're still getting webRequest callbacks or know the limitations
3. conversion to DNR rules does not hurt
4. avoid racy behaviour (receiving headers vs getting stylesheet for the URL)