#3590572 Indicate translation availability per language in the Canvas language switcher dropdown

• Updated the layout controller to include translation info. Note there is an additional operations property that will be used for contextual operations, made available in a manner where we can introduce an alter hook and support functionality that @tedbow mentioned needing in the near future.

Testing instructions

• Install Drupal with the minimal profile
• Enable the canvas, canvas_test_sdc, and canvas_test_recipe modules: drush en canvas canvas_test_sdc canvas_test_recipe
• Apply the test translation recipe: php core/scripts/drupal recipe modules/contrib/canvas/tests/fixtures/recipes/test_translation -vvv
• Navigate to canvas/editor/canvas_page/1
• Verify the Language Selector dropdown is visible on the right side of the top bar (showing "English")
• Verify the English and French have checkmarks to indicate available translations, and that Spanish does not have a checkmark

Closes #3590572