Document cross-SDK guarantees for DAML Script

[cocreature]

The daml-script type currently does not work across SDK versions. It is actually already filtered out from data-dependencies because by accident it is recognized as an old-style typeclass (it is a record with a function that takes a unit argument). We could fix the data-dependencies part and expose it but then you just end up with two Script types which isn’t helpful in any way. Instead, we should filter it out properly (to make sure it stays filtered out if we change the definition and it no longer ends up looking like a typeclass) and document this.

[cocreature]

We do support this in data-dependencies now so this is just like any other type that isn’t compatbile across SDK versions. I don’t think there is anything special about this that we should document.