* Atomically check for processing lock in Move handler

* Prevent race condition when creating account migrations

Fixes #15595

* Add tests

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

There are edge cases where requests to certain hosts timeout when
using the vanilla HTTP.rb gem, which the goldfinger gem uses. Now
that we no longer need to support OStatus servers, webfinger logic
is so simple that there is no point encapsulating it in a gem, so
we can just use our own Request class. With that, we benefit from
more robust timeout code and IPv4/IPv6 resolution.

Fix #14091

Fix #11913

Fix #10736

- Change data export to be available for non-functional accounts
- Change non-functional accounts to include redirecting accounts