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.
use sendRoomKeyRequest with a new resend flag, instead of cancelRoomKeyRequest,
when requesting keys, so that we make sure that we send a new request if there
is no previous request
fixes https://github.com/vector-im/riot-web/issues/6838
* Start a new Olm sessions with a device when we get an undecryptable
message on it.
* Send a dummy message on that sessions such that the other end knows
about it.
* Re-send any outstanding keyshare requests for that device.
Also includes a unit test for megolm that isn't very related but came
out as a result anyway.
Includes https://github.com/matrix-org/matrix-js-sdk/pull/776
Fixes https://github.com/vector-im/riot-web/issues/3822
Hopefully this will fix the vector-web test failures (the
OutgoingRoomRequestManager throws an exception because the indexeddb is being
deleted just as it's getting started).