fix extracting cross-posts from activitypub sites

[hdk5]

Follow up to 750d3bc.

Misskey and mastodon allow "retweets" not only from other instances running the same software, but also retweets from each other and other software implementing ActivityPub protocol.

Consider adding support for those kind of URLs:

1. Same instance misskey renote (e.g. https://misskey.io/notes/9tb8t7phwzd80f0c)
2. Cross instance misskey renote (which is a different thing from "note pulled from remote instance") (e,g. https://misskey.io/notes/9inijumei6)
3. Remote note from known mastodon instance (pawoo/baraag) on misskey (e.g. https://misskey.io/notes/9t9r29xcbqs300th)
4. Cross instance mastodon boost (e.g. https://pawoo.net/@akableak@baraag.net/112422466644091163)
5. Cross instance cross software mastodon boost (e.g. https://pawoo.net/@fuwafuwafox@misskey.io/112441725067458010)
6. Posts/reposts involving unknown mastodon instances, or completely different software (no example)

4 and 5 redirect to original when opened directly, but are possible to open on remote's web ui if found on retweeter's profile,

Additional comment regarding 750d3bc#diff-28621ec4edc016d9ec0e33f0bdac376f013cfca317bbf2bc977e56c96610dfc6R91:
I don't think it makes sense to include foreign user url (i.e. https://misskey.io/@orizanin@nijimiss.moe) here. Instead, there should be id link on the original instance there (so https://nijimiss.moe/users/01GSP49ET693HTB3QE8G5ZXJ8W in this case)