Fix superclass constant resolution to avoid self-reference

[pvcresin]

This change fixes superclass constant resolution for nested class Foo < Foo so the resolver no longer picks the class currently being defined.
It introduces an exclusion cpath on StaticRead and applies it from ClassNode#define0 before re-resolving the superclass read.
A regression scenario was also added at scenario/regressions/superclass-self-reference.rb.

## update: model.rb
class Foo
  def value = 1
end

module Bar
  class Foo < Foo
  end
end

## update: test.rb
def call
  Bar::Foo.new.value
end

With this case, TypeProf now consistently infers def call: -> Integer instead of falling back to untyped.