C#: Consider changing `List` parameters to e.g. `IEnumerable`

[dicej]

Per dotnet/runtimelab#2614 (comment), List parameters are often unnecessarily restrictive -- callers might want to pass collections of other types without converting them to Lists first.

[pavelsavara]

note that IEnumerable doesn't have Count/Length but you will likely need to know it upfront to allocate for marshaling. So maybe other interfaces I mentioned would be better fit. Or you could even generate multiple signatures.

[pavelsavara]

I don't know if we also marshal arrays of structs and primitive types (not resources), but in such case Span<T> and ReadOnlySpan<T> are better choices. Because those could live on stack. It would also help with stream APIs