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`

test/test-utils/client.ts

@@ -64,6 +64,8 @@ export class MockClientWithEventEmitter extends EventEmitter {
         getUserId: jest.fn().mockReturnValue(aliceId),
     });
  * ```
+ *
+ * See also `stubClient()` which does something similar but uses a more complete mock client.
  */
 export const getMockClientWithEventEmitter = (
     mockProperties: Partial<Record<keyof MatrixClient, unknown>>,
@@ -158,6 +160,7 @@ export const mockClientMethodsCrypto = (): Partial<
         getSessionBackupPrivateKey: jest.fn(),
     },
     getCrypto: jest.fn().mockReturnValue({
+        getUserDeviceInfo: jest.fn(),
         getCrossSigningStatus: jest.fn().mockResolvedValue({
             publicKeysOnDevice: true,
             privateKeysInSecretStorage: false,