[TwigBundle] Adds service check for extension loading
merged branch jfsimon/issue-6238 (PR #7373)

This PR was squashed before being merged into the master branch (closes #7373).

Commits
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e372183 [TwigBundle] Adds service check for extension loading

Discussion
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[TwigBundle] Adds service check for extension loading

This PR adds following checks:
*  `twig.extension.form` extension is loaded if `form.extension` service is defined
*  `twig.extension.trans` extension is loaded if `translator` service is defined

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6238