Add visual tests for table visualisation (#18826)

* Add visual tests for table visualisation

* Wait until spinner disappears

frontend/test/metabase-visual/visualizations/table.cy.spec.js

+import { restore, openOrdersTable, modal } from "__support__/e2e/cypress";
+
+describe("visual tests > visualizations > table", () => {
+  beforeEach(() => {
+    cy.intercept("POST", "/api/dataset").as("dataset");
+    restore();
+    cy.signInAsNormalUser();
+
+    openOrdersTable();
+    cy.wait("@dataset");
+    cy.findByTestId("loading-spinner").should("not.exist");
+  });
+
+  it("ad-hoc", () => {
+    cy.percySnapshot();
+  });
+
+  it("saved", () => {
+    saveQuestion();
+    cy.percySnapshot();
+  });
+});
+
+function saveQuestion() {
+  cy.findByText("Save").click();
+  modal().within(() => {
+    cy.button("Save").click();
+  });
+  modal()
+    .findByText("Not now")
+    .click();
+}