Remove "Controllers extends ContainerAware" best practice
feature #4009 Remove "Controllers extends ContainerAware" best practice (tgalopin)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4009).

Discussion
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Remove "Controllers extends ContainerAware" best practice

As discussed in https://github.com/symfony/symfony-docs/issues/4008, I remove the best practice consisting of extending ContainerAware instead of base Controller class to improve DX.

Commits
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992033f Remove "Controllers extends ContainerAware" best practice