feat: add lsp support for type classes

[jaschdoc]

• [ ] Rename classes
• [ ] Type constraints (Semantic tokens for these or what is meant by this?)

Test program

def main(): Unit & Impure =
    Tester.p();
    println("${A.b(5)}")

pub class A[t] {
    pub def b(t: t): t with ToString[t] = t
}

instance A[Int32]

other file

namespace Tester {

    pub def p(): Unit & Impure =
        println("${A.b(15)}")

}

Closes #1525

[mlutze]

Also please test this with namespaces. Source locations are tricky when you have e.g. instance N.C[a]

[magnus-madsen]

I will break the original task down into smaller tasks.