Simplify references to VerificationRequest (#11045)

* Use new `VerificationRequest.getQRCodeBytes()`

* Use new `VerificationRequest.otherDeviceId`

* Remove references to `VerificationRequest.channel`

* Replace references to `VerificationRequest.{requesting,receiving}UserId`

Normally these are guarded by `request.initiatedByMe` so we can trivially
replace it with `request.otherUserId` or `client.getUserId()`. In one place we
actually need to apply some logic.

* increase test coverage

* Even more test coverage

* Even more test coverage

src/components/views/right_panel/EncryptionPanel.tsx

@@ -165,7 +165,7 @@ const EncryptionPanel: React.FC<IProps> = (props: IProps) => {
                 onClose={onClose}
                 member={member}
                 request={request}
-                key={request.channel.transactionId}
+                key={request.transactionId}
                 inDialog={layout === "dialog"}
                 phase={phase}
             />