Check new C# params interop with F#

[psfinaki]

From #16967:

We need to assess which features we will need to support in F# 9
Params collections: developers can now put params in front of many more collection types in signatures including Span.
Make sure F# compiler can work with those, even if F# user has to construct collection type by hand.

So:

1. If it doesn't work, make it work
2. It it does work, document how it works
3. Add tests regardless

[psfinaki]

The lang suggestion is here.