[Drupal 12 compatibility] Symfony 8 removes fallback Request::get()

Problem/Motivation

Since symfony/http-foundation 7.4: Request::get() is deprecated, use properties ->attributes, ->query or ->request directly instead. See Symfony issue, [HttpFoundation] Deprecate Request::get() in favor of using properties ->attributes, query or request directly

The Embed module's preview controller uses Request::get() when we accept data via GET; in Symfony 8 this will no longer be allowed.

See similar core issue #3555532: Since symfony/http-foundation 7.4: Request::get() is deprecated, use properties ->attributes, query or request directly instead..

Steps to reproduce

Attempt to use this module with Drupal 12 + Symfony 8. This will throw the exception Error: Call to undefined method Symfony\Component\HttpFoundation\Request::get() in Drupal\embed\Controller\EmbedController->preview()

Proposed resolution

Use the method for retrieving get parameters supported since Symfony 2, $request->query->get

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A