Add test to check drupal working before installing genpass

Without Generate Password event installed, testing is unable to access admin/config/people/accounts in current or next minor.

From the new NotInstalledTest.php =>

  /**
   * Check to see that Drupal core is working, then install genpass.
   */
  public function testDrupalWorkingWithoutAndWith(): void {
    // Check that Drupal is working before installing Generate Password.
    // THIS IS WHAT FAILS! UNABLE TO ACCESS THIS PAGE?
    $this->drupalGet('admin/config/people/accounts');
    $this->assertSession()->statusCodeEquals(200);

    // Install Generate Password.
    $this->assertTrue(
      \Drupal::service('module_installer')
        ->install(['genpass']),
      'Failed to install Generate Password module.'
    );

    // Check that the same page is still accessible.
    $this->drupalGet('admin/config/people/accounts');
    $this->assertSession()->statusCodeEquals(200);

    // Check all of the form changes.
    $this->assertSession()->pageTextContains('Account settings');
    $this->assertSession()->pageTextContains('Generate Password - User Account Registration');
    $this->assertSession()->pageTextContains('User password entry');
    $this->assertSession()->pageTextContains('Admin password entry');
    $this->assertSession()->pageTextContains('Generated password length');
    $this->assertSession()->pageTextContains('Generated password display');
  }

All tests work perfectly locally so this is only on the testing infrastructure that things are broken.

The act of logging into drupal as an administrator with ['administer account settings', 'administer users'] and accessing $this->drupalGet('admin/config/people/accounts'); is causing a 500 error. This should be without genpass installed unless I am mistaken about the $this->modules array, from which I have removed genpass. Should check on that.

Added to the test; genpass is not installed at the start, and drupal core is still giving 500 error on admin/config/people/accounts, NOT on admin.

Forcing twig to 3.14.0 fixes it here, and all the live sites I just dutifully updated just today.

Fix will be done in #3485956: Recursion limit exceeded with Twig v3.14.1 when editing a node or a block.

Change of title to reflect the actual change as a result of this isssue; to avoid going down the rabbit hole of suspecting something wrong with the module, make sure that Drupal works before genpass is installed.