Drop twig deferred blocks and deprecated pimcore_* twig extension calls

[markus-moser]

Related to pimcore/pimcore#17444

• Deferred blocks are not needed, everthing works without the deferred attribute too. As this extension does not work with twig >=3.9.0 it's removed now.

  • The only exception could be if someone extends the CMF layout in custom code and calls the pimcore_head_link extension within the content block. In that case the call would need to be moved outside of the content block. But that's a real edge case!

• The deprecated usage of pimcore_head_script().captureStart() is replaced with an alternative approach.

[markus-moser]

As without a updated twig version we have security problems (see pimcore/pimcore#17457 (comment)) we need to remove the deferred blocks extension right now as bugfix as it is incompatible with current versions.