update only if i'm the touched item

[DavidBabel]

see #1103

[tlenclos]

We have a big form in our app and this PR is improving performance 👍
The user experience is still very bad for our user but this is a move in the right direction.

[DavidBabel]

@tlenclos be carefull, this "quick win fix" may loss some features of Formik, i'm not enough comfortable with the library to know yet.

the real performance improvement will come from #1103, but it's a deeper change.

[jaredpalmer]

While this would work for Formik v1's registration, i think it has some problems with how I plan to do field registration in v2. In v1 we naively assume there is 1:1 relationship with fields to components. This is why we didn't implement ErrorMessage with field (because that would break). However, in v2, this won't be the case. This trick could still work though, the value would just include some kind of random number or uuid.

[jaredpalmer]

However, we may not even really need registration (or rather it may become hard to understand) with fiber/suspense and with upcoming useField. Not sure yet.

[jaredpalmer]

Closing in favor of #2749