[Process] create_new_console option only on Windows

[thomas-l]

No description provided.

[thomas-l]

I'm not sure whether it has always been the case for older versions of PHP proc_open function. Tell me if I should anyway make a PR against the oldest branch with the options.

[javiereguiluz]

Thomas, thanks and congrats on your first Symfony Docs contribution 🎉

I wasn't aware of this limitation, so it's a good idea to mention it explicitly in the docs.
Note that while merging, I expanded your original caution a bit more to explain more in detail this limitation (See c9e0e92).

Finally, we merged this in 5.4 branch and all the upper maintained branches. Thanks!

[thomas-l]

I was in a rush and did not manage to expand my short caution in a decent way! I'll take the time to do better next time 😊