After a successful verification with ourselves, request the key
backup key too and restore a key backup if we get it.
Also cache the key backup key when we cache the SSK & USK so we have
it available to share.
Fixes https://github.com/vector-im/riot-web/issues/12704
Rather than accessing private method to get the secret storage
object (this was a bit confusing when I grepped for 'requestSecret'
and didn't find anything).
* For self-verifications, also request keys from the other device
* removed some XXX's so the editor doesn't think it's three issues
* add methods to access key cache callbacks
Instead, call onVerifierFinished from the verifier on the request
so we can internally mark it as done. This flag is not persisted,
but we don't have historical (persisted) to-device requests anyway.
if we get a .start event from the other party and we've also sent one,
the .start event with the sender that is first in sorting order should
be taken, and the other one ignored.
At the point where we will receive it, the verifier has already
been returned from beginKeyVerification, so we'll need to switch
start event internally, and retry the verification, now on the
receiver (sending .accept) side instead of initiator side
(sending .start).
The bulk of this is just export/import changes, though there's a couple pieces to highlight:
* We no longer use default exports. This is because it's discouraged by the JS community, though not in any official capacity.
* We now use `polyfillSuper` for some prototype inheritance because the tests, and sometimes webpack, break on "cannot call EncryptionAlgorithm without 'new'". It's very much a workaround, and definitely not needed when we use real classes.
There is some import shuffling to help keep the imports clean - this was done by my IDE.
