This lays a foundation for redirecting all the traffic through the new store, but for now the core parts of the app need to stop caring if the right panel is open.
This adds dialogs for creating and accessing secret storage via a passphrase or
recovery key. These flows are adapted from the ones used for key backup.
With this version of babel (via babel-eslint), eslint now fails
with a somewhat confusing, "Unexpected reserved type number"
(from the flow plugin...) if you get this wrong.
Fixes https://github.com/vector-im/riot-web/issues/11547
Steps taken:
* Convert `E2ePadlock` to a class-style component so the hover state can be tracked (tooltips).
* Convert the image mask to a background image to keep the `!` in the shield.
* Update copy.
This is not part of any designs, so it may be short-lived, but it's quite handy
for diagnosing issues with cross-signing at least while the feature is in
development.
Fixes https://github.com/vector-im/riot-web/issues/11496
Fixes https://github.com/vector-im/riot-web/issues/11385
Fixes https://github.com/vector-im/riot-web/issues/10007
Fixes https://github.com/vector-im/riot-web/issues/9769
React does (kinda) bind `this._isUnmounting` for us in the context of the EventTile, but the EventTile then passes the function straight through to the ReadReceiptMarker component, which then binds it in the context of EventTile. This results in `this._mounted` being falsey all the time, preventing the ReadReceiptMarker from hitting the code where it updates rrInfo in its unmount.
The velocity stuff is smart enough to realize that it has a read receipt and shuffles everything over by one, but when it goes to check the starting height (which will be null/undefined because the RRMarker didn't update it) it assumes it has never seen the receipt before and appends it again - this is what causes some holes/stacking.
By forcefully binding the `this._isUnmounting` function we ensure that the `this._mounted` variable is correctly referenced in the context of the MessagePanel, allowing the RRMarker to update its position, and therefore allowing the velocity behaviour to be consistent.
Fixes https://github.com/vector-im/riot-web/issues/11518
This also fixes a bug where the the theme logic can incorrectly get stuck in the light theme - the ThemeController was overriding *all* values, not just supposed themes. Null values aren't overridden so that the various theme logic bits don't assume the user has chosen the light theme explicitly.
