When calling `getDeviceList`, wait for the devices to be fetched
Otherwise a race condition might occur, whereby a new device gets
created in the collection, and then removed again as the collection is
replaced with the values fetched from the browser-storage cache.
Also created `converse-omemo-fingerprints` component to asynchronously
render fingerprints in the user details modal. Was done as part of this
commit because due to `getDeviceList` being async, the relevant test for
the modal were also failing
Had to make various other changes due to incompatibilities.
- Use the new `lit` package instead of `lit-html` or `lit-element`
- Drop `haunted` since it breaks the rules by specifying `type: module`
but then doesn't import with file extensions
- Use Sass Dart instead of node-sass (fixes#2445)
- Upgrade Karma
- Update to the latest @converse/skeletor (which uses mergebounce to batch writes)
- Flush storage before logging out
- Flush when reloading the tab
- Create initStorage method
