[code-infra] Add react-testing-library eslint plugin

[oliviertassinari]

configure eslint-plugin-testing-library and fix issues

See mui/toolpad#3648 as an implementation example.

Could also be helpful in:

• 1. [code-infra] In react tests, clean up our act() #174
• 2. Use screen at the import level, not the mounting point level:

-import { render } from '@testing-library/react';
+import { render, screen } from '@testing-library/react';

   test('renders content correctly', async () => {
-    const { getByText } = render(<AppProvider>Hello world</AppProvider>);
+    render(<AppProvider>Hello world</AppProvider>);

-    expect(getByText('Hello world')).toBeTruthy();
+    expect(screen.getByText('Hello world')).toBeTruthy();
   });
 });

For example mui/material-ui#41061 (comment)

• 3. Use user at the import level, not the mounting point level: [core] Support @mui/material@6 peer dependency mui-x#14142 (comment). Actually maybe not: [code-infra] Optimize @testing-library/user-event material-ui#43804 (comment).