Cypress test for incoming user verification

[richvdh]

... because it turned out we didn't have one, and it was broken (element-hq/element-web#26245)

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This change is marked as an internal change (Task), so will not be included in the changelog.

[richvdh]

Looks like this might have caused some brokenness:

  1) Cryptography
       should allow verification when there is no existing DM:
     CypressError: `cy.then()` failed because you are mixing up async and sync code.

In your callback function you invoked 1 or more cy commands but then returned a synchronous value.

Cypress commands are asynchronous and it doesn't make sense to queue cy commands and yet return a synchronous value.

You likely forgot to properly chain the cy commands using another `cy.then()`.

The value you synchronously returned was: `!dvafiRlnhyVMVzYeOY:localhost`
      at getRet (http://localhost:8080/__cypress/runner/cypress_runner.js:145225:78)
      at tryCatcher (http://localhost:8080/__cypress/runner/cypress_runner.js:18744:23)
      at Promise.attempt.Promise.try (http://localhost:8080/__cypress/runner/cypress_runner.js:16018:29)
      at Context.thenFn (http://localhost:8080/__cypress/runner/cypress_runner.js:145234:63)
      at Context.then (http://localhost:8080/__cypress/runner/cypress_runner.js:145483:21)
      at wrapped (http://localhost:8080/__cypress/runner/cypress_runner.js:160816:19)
  From Your Spec Code:
      at createSharedRoomWithUser (webpack:///./cypress/e2e/crypto/utils.ts:207:83)
      at Context.eval (webpack:///./cypress/e2e/crypto/crypto.spec.ts:244:0)

  2) Cryptography
       event shields
         "before each" hook for "should show the correct shield on e2e events":
     CypressError: `cy.then()` failed because you are mixing up async and sync code.

In your callback function you invoked 1 or more cy commands but then returned a synchronous value.

Cypress commands are asynchronous and it doesn't make sense to queue cy commands and yet return a synchronous value.

You likely forgot to properly chain the cy commands using another `cy.then()`.

The value you synchronously returned was: `!MWXWaYbpZQERcdvdRh:localhost`

Because this error occurred during a `before each` hook we are skipping the remaining tests in the current suite: `event shields`
      at getRet (http://localhost:8080/__cypress/runner/cypress_runner.js:145225:78)
      at tryCatcher (http://localhost:8080/__cypress/runner/cypress_runner.js:18744:23)
      at Promise.attempt.Promise.try (http://localhost:8080/__cypress/runner/cypress_runner.js:16018:29)
      at Context.thenFn (http://localhost:8080/__cypress/runner/cypress_runner.js:145234:63)
      at Context.then (http://localhost:8080/__cypress/runner/cypress_runner.js:145483:21)
      at wrapped (http://localhost:8080/__cypress/runner/cypress_runner.js:160816:19)
  From Your Spec Code:
      at createSharedRoomWithUser (webpack:///./cypress/e2e/crypto/utils.ts:207:83)
      at Context.eval (webpack:///./cypress/e2e/crypto/crypto.spec.ts:253:0)