Enable --new-type-inference by default

[ilevkivskyi]

I think we should be able to do this in mypy 1.7.0. After enabling this by default, new inference scheme will still be used as a fallback. And we can make it the main mechanism later on.

This is a follow-up for series started by #15287

[ilevkivskyi]

cc @JukkaL

Is there any way for me, as a plain-old user, to opt-in ahead of time? I see a commandline option, but didn't find anything in the configuration reference.

[ilevkivskyi]

I am not 100% sure, but you can try new_type_inference = true in the main section of config file. This flag is not supported for per-module configuration. But also I am going to make it default in master this or next week (and it will be released in 1.7.0).