Check type for forward reference definition

Check type for forward reference definition

The types of forward references are checked that they match with other
uses, but they do not check they match with the definition.

    func @forward_reference_type_check() -> (i8) {
      br ^bb2

    ^bb1:
      return %1 : i8

    ^bb2:
      %1 = "bar"() : () -> (f32)
      br ^bb1
    }

Would be parsed and the use site of '%1' would be silently changed to
'f32'.

This commit adds a test for this case, and a check during parsing for
the types to match.

Patch by Matthew Parkinson <mattpark@microsoft.com>

Closes D79317.