[DependencyInjection] Improve url env var processor with type cast

[noniagriconomie]

Hi

I've tried on my symfony app v4.4, the env(url:FOO) env processor reading the doc at https://symfony.com/doc/4.4/configuration/env_var_processors.html

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Without the changes proposed in this PR, I got:

• with definition like this in an app.yaml file
  • service.port: '%env(key:port:url:SERVICE_DSN)%'
• the error
  • Invalid type for path "service.port". Expected one of "bool", "int", "float", "string", but got one of "bool", "int", "float", "string", "array".

but it works only like this:

• service.port: '%env(int:key:port:url:SERVICE_DSN)%'
• same with string: for example a key:user or a key:pass fields from the url processor

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Thus I am proposing this PR to correct the usage of this processor
If I am doing something wrong/incorrect, please answer what/why and feel free to close this PR!

Thank you :)

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Symfony 4.4.29
PHP 7.4.22

[javiereguiluz]

Nice fix and perfectly explained ❤️ Thanks Antoine!