When inductives are indirectly mutually recursive, say `inductive T | t
(args: List T)` instead of `inductive T | t (arg : T)`, Lean would fail
to find an instance of Hashable for `T` because it was not yet defined.
This commit makes sure that the deriving handler adds a needed Hashable T
instance to the local scope so that Hashable.hash can be resolved
recursively.
Most notable change: `Quote` is now parameterized by the target kind.
Which means that `Name` etc. could actually have different
implementations for quoting into `term` and `level`, if that need ever
arises.
change the generated to code recursively call the fields of recursive
and mutually recursive types. Currently, this can emit `partial`
functions due to lacking structural recursion. The code is prepared,
however, for the full implementation and can be trivially turned into
code generating non-`partial` functions
