FIR: only allow member val initialization through this@T

class C {
    val x: Int
    init {
      // valid ways to initialize:
      x = 1
      this@C.x = 1
      // invalid:
      someOtherC.x = 1
      run { /*this@run.*/x = 1 }
      val self = this
      self.x = 1
    }
  }

compiler/fir/analysis-tests/testData/resolve/cfa/reassignOfNonMemberProperty_lateInitialization.kt

@@ -15,11 +15,20 @@ class Some {
     }
 
     val a: String = run {
+        // these are all on this@run, which is not guaranteed to be this@Some
+        <!VAL_REASSIGNMENT!>x<!> = "error"
+        <!VAL_REASSIGNMENT!>y<!> = "error"
+        <!VAL_REASSIGNMENT!>z<!> = "error"
+        "hello"
+    }
+
+    val b: String = 123.run {
+        // now this@run is an Int, so these are on this@Some
         x = "error"
         y = "ok"
         y = "error"
         <!VAL_REASSIGNMENT!>z<!> = "error"
-        "hello"
+        "there"
     }
 
     init {