[DependencyInjection] fix a regression introduced in #9807

Always dump the fully qualified class name, to support dumping containers in a namespace.
bug #9812 [DependencyInjection] fix a regression introduced in #9807 (realityking)

This PR was merged into the 2.5-dev branch.

Discussion
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[DependencyInjection] fix a regression introduced in #9807

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

As @stof pointed out in #9807 we always need to dump the fully qualified class name, to support dumping containers in a namespace.

Commits
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0d78776 [DependencyInjection] fix a regression introduced in #9807