…e ENV (Plopix)

This PR was merged into the master branch.

Discussion
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Provides a way to override cache and log folders from the ENV

Related to this new feature symfony/symfony#37114.

But I wonder if we have not oversimplified this PR: symfony/symfony#37114

Actually doing the documentation #13787 I figured that with #37114 we removed the important split per `env`.

In development mode (docker or not) we could definitely have the same project working in N Symfony different environments and this new `APP_CACHE_DIR` will only set the same path for all environments.

That would be manageable in the Virtualhost but in CLI that would be a pain to manage.
Also, we could rely on the DotEnv mechanism, but that could be really easy to forget.

I wonder if we should not change the code to: symfony/symfony#37232

Depending on the decisions I will update the doc here.

Commits
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88b081c Provides a way to override cache and log folders from the ENV