Add cy.viewRoomById command (#11317)

... and use it to fix a racy composer test.

Fixes https://github.com/vector-im/element-web/issues/25527

cypress/support/views.ts

@@ -29,6 +29,15 @@ declare global {
              */
             viewRoomByName(name: string): Chainable<JQuery<HTMLElement>>;
 
+            /**
+             * Opens the given room by room ID.
+             *
+             * This works by browsing to `/#/room/${id}`, so it will also work for room aliases.
+             *
+             * @param id
+             */
+            viewRoomById(id: string): void;
+
             /**
              * Returns the space panel space button based on a name. The space
              * must be visible in the space panel
@@ -57,6 +66,10 @@ Cypress.Commands.add("viewRoomByName", (name: string): Chainable<JQuery<HTMLElem
     return cy.findByRole("treeitem", { name: name }).should("have.class", "mx_RoomTile").click();
 });
 
+Cypress.Commands.add("viewRoomById", (id: string): void => {
+    cy.visit(`/#/room/${id}`);
+});
+
 Cypress.Commands.add("getSpacePanelButton", (name: string): Chainable<JQuery<HTMLElement>> => {
     return cy.findByRole("button", { name: name }).should("have.class", "mx_SpaceButton");
 });