Associate word refer with 'search for references in Scala code' functionality

[kiritsuku]

The following test for NlqTest does not pass yet:

  @Test
  def xxx(): Unit = {
    indexData(Artifact(Project("p"), "o", "n", "v1"),
      "x.scala" → """
        class A {
          def f = 0
          val a1 = f
          def a2 = {
            val a3 = 0
            f
          }
          var a4 = 0
        }
        trait B {
          def b1: A
          def b2 = b1.f
        }
      """)
    nlqRequest("list names of decls that refer to def A.f").sortedAsList === Seq(
      "a1",
      "a2",
      "b2"
    )
  }

The word refer needs to be associated with the code that searched for references within Scala code.