Support type parameters in record type spread

[cristianoc]

https://forum.rescript-lang.org/t/ann-enhanced-ergonomics-for-record-types/4480/8?u=cristianoc

Example:

type x<'a> = {
  a: 'a,
  b: int,
}

type y<'a> = {
  ...x<'a>,
  c: float,
}

There are few choices possible here. The simplest, most restrictive one is:

• y has the same number and names of type parameters as x, then there's nothing else to check.

[fhammerschmidt]

Will it really be only in version 12? Currently I am spreading MUI's useAutocomplete props into the MUI Autocomplete props.

type autocompleteProps<'a> = {
  ...UseAutocomplete.props<'a>,
  ...
}

But that gives me an unbound type parameter error, as expected.

My current workaround makes me spread only a subset of the props that contain no type parameters, while I add the remaining props manually to the Autocomplete props.

I am not sure if I there is a need to support different numbers and names of type parameters. It would be cool if the simplest form could be added to v11 still.

[cristianoc]

Kind of follows after #6293
Once that's solved, this can be revisited.

[cristianoc]

Investigation here: #6309