lambda targets that are not `universe` do not work inside their outer features

[fridis]

lambdas targets that are defined inside the features they are used in currently do not work (since the outer type is xyz.this and the lambda will be created in xyz.fun#123).

Try this:

o is
  F ref is
    c(a i32) i32 : fuzion.lambda_target => abstract

  _ F := x->x+1   # causes error!!!

_ o.F := x->x+1   # works fine

which produces an error for the use of F as a target for a lambda within o:

 > ./build/bin/fz test_lambda.fz

/home/fridi/fuzion/fuzion/test_lambda.fz:5:3: error 1: Incompatible types in assignment
  _ F := x->x+1   # causes error!!!

assignment to field : 'o._'
expected formal type: 'o.this.F'
actual type found   : 'o.this.λ'
assignable to       : 'Any',
                      'o.F',
                      'o.this.λ'
for value assigned  : 'x->x+1'
To solve this, you could change the type of the target 'o._' to 'o.this.λ' or convert the type of the assigned value to 'o.this.F'.

one error.