Use options.cryptoCallbacks for things that require information
from the app rather than events, since events can have zero, one
or many listeners and the emitter doesn't know how many, so if
nobody's listening then we would have just waited forever for a
response.
Also a collection of other changes like renaming 'fu' to 'firstUse'
The code to migrate from the `sessionStore` to `cryptoStore` originally appeared
in https://github.com/matrix-org/matrix-js-sdk/pull/584 (2017-12-06). At this
point, it seems safe to assume most sessions that need migrating have already
done so. Removing this code simplifies store handling and removes the
`sessionStore` from most places in JS SDK.
Standardize on importing `olm-loader` rather than pasting the same boilerplate
in different tests. Importantly, `spec/unit/crypto.spec.js` did not include any
loading approach, so it would only find Olm if some other test loaded it first.
Signed-off-by: J. Ryan Stinnett <jryans@gmail.com>
