Kill off references to deprecated getStoredDevice and getStoredDevicesForUser (#11152)

* Use new `CryptoEvent.VerificationRequestReceived` event

https://github.com/matrix-org/matrix-js-sdk/pull/3514 deprecates
`CryptoEvent.VerificationRequest` in favour of
`CryptoEvent.VerificationRequestReceived`. Use the new event.

* Factor out `getDeviceCryptoInfo` function

I seem to be writing this logic several times, so let's factor it out.

* Factor out `getUserDeviceIds` function

Another utility function

* VerificationRequestToast: `getStoredDevice` -> `getDeviceCryptoInfo`

* SlashCommands: `getStoredDevice` -> `getDeviceCryptoInfo`

* MemberTile: `getStoredDevicesForUser` -> `getUserDeviceIds`

* Remove redundant mock of `getStoredDevicesForUser`

src/SlashCommands.tsx

@@ -70,6 +70,7 @@ import { leaveRoomBehaviour } from "./utils/leave-behaviour";
 import { isLocalRoom } from "./utils/localRoom/isLocalRoom";
 import { SdkContextClass } from "./contexts/SDKContext";
 import { MatrixClientPeg } from "./MatrixClientPeg";
+import { getDeviceCryptoInfo } from "./utils/crypto/deviceInfo";
 
 // XXX: workaround for https://github.com/microsoft/TypeScript/issues/31816
 interface HTMLInputEvent extends Event {
@@ -1031,7 +1032,7 @@ export const Commands = [
 
                     return success(
                         (async (): Promise<void> => {
-                            const device = cli.getStoredDevice(userId, deviceId);
+                            const device = await getDeviceCryptoInfo(cli, userId, deviceId);
                             if (!device) {
                                 throw new UserFriendlyError(
                                     "Unknown (user, session) pair: (%(userId)s, %(deviceId)s)",