Provide integration with Clear-Site-Data

[annevk]

Based on https://w3c.github.io/webappsec-clear-site-data/#clear-cookies it looks like we need to be able to delete cookies given a registrable domain.

It's not entirely clear how Clear-Site-Data integrates with partitioning though so it is likely more subtle than that: w3c/webappsec-clear-site-data#72.

There's also some concerns about how this works in general, seemingly without resolution: w3c/webappsec-clear-site-data#55.

[annevk]

Make sure this also works for https://github.com/privacycg/nav-tracking-mitigations. See discussion in privacycg/nav-tracking-mitigations#78 for context.