Deal as well with sending key if key is outdated in the providers nicknym.

- Resolves: #8819, #8832

- remove premature optimization for fast-notifies. blobs will cover
that, no point in maintaning the optimization at the price of creeping
complexity.

- Create the 'Sent folder' ourselves to avoid pixelated hitting a bug in
  mailbox creation.
- I believe there's still a problem with bitmask desing for the adaptor
  (in get-or-create mailbox). This needs further tests.
- Case manipualation to avoid having a 'Sent' and 'SENT' folder when
  Thunderbird and Pixelated write to those.
- Further hacks to monkeypatch the leap-mail-adapter that Pixelated
  uses (make them reuse the account instance!). This is getting insane,
  I am really looking forward to the fork.
- Duly note our technical debt in the area of Pixelated integration.
  Keeping the Pixelated codebase untouched for a long time will
  backfire. As far as I've noticed, we have a basic violation of the
  assumptions about a single-instance writes and notifications to all
  listeners. As commented in the commit, this should go either for a
  guarantee that only one account object is created per user (creating
  it in the bootstrapping process in bitmask), or for the opposite
  direction in which the listeners are communicated in some other way
  (zmq events, for instance).
- In any case, it's strongly recommended to deduplicate the Pixelated
  libraries as soon as possible and make Pixelated use a better defined
  set of Bitmask's public apis.
- Modify the wrapper create methods so that they return the modified
  wrapper itself.

- Resolves: #8903, #8904

When setting the listeners in the IMAP Folder, we avoid setting more
than one listener for the same imap mailbox (because in some situations
we were registering way too many listeners).

this was making the pixelated inbox registering the notification and
therefore the imap mailbox not being registered.

this MR also refactors the way pixelated is initialized, so that it
avoid creating a second Account instance. In this way, we make sure that
the pixelated mua and the imap server share the same collections for a
given mailbox, and therefore any of the two is able to get a
notification whenever the other adds a message to the mailbox.

- Resolves: #8846, #8798