[DependencyInjection] Fix ContainerBuilder stats env usage with enum

[alamirault]

Q	A
Branch?	6.2
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets	Fix #48498
License	MIT
Doc PR	symfony/symfony-docs#...

Without patch:

[
    'enum:Symfony\Component\DependencyInjection\Tests\Fixtures\StringBackedEnum:foo' => 0,
    'Bar' => 1,
]

With patch:

[
    'enum:Symfony\Component\DependencyInjection\Tests\Fixtures\StringBackedEnum:foo' => 1,
    'Bar' => 1,
]

[GromNaN]

Thank you for the test.
For reviewers, this regex was introduced by #47176

[GromNaN]

The regex is also in MergeExtensionConfigurationPass.

[nicolas-grekas]

Looking why we forgot that in #46564, I think the correct patch is to add \\ to the strtr on this line:
https://github.com/symfony/symfony/blob/6.2/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php#L52

[nicolas-grekas]

(I implemented the change I suggested)

[nicolas-grekas]

Thank you @alamirault.

[alamirault]

(I implemented the change I suggested)

Thanks Nicolas 😄