Rename `Kind`

[varkor]

A Kind is not really a kind: it's a term (e.g. a particular type, a particular lifetime or a particular value). However, "Term" is overloaded as terms are usually values of particular types (which is just one case here). KindedTerm has been suggested.

[oli-obk]

For me, this doesn't clarify anthing. It just means I'm gonna learn another name that means nothing.

I liked the GenericArg suggestion, since it matches the AST/HIR naming for the equivalent values.

[varkor]

I liked the GenericArg suggestion, since it matches the AST/HIR naming for the equivalent values.

That could work 👍