Extraction Engine: Respect smart casts applied to "this" references

#KT-7447

idea/testData/refactoring/extractFunction/parameters/extractThis/implicitThisWithSmartCast.kt

@@ -0,0 +1,17 @@
+// SUGGESTED_NAMES: i, getB
+// PARAM_DESCRIPTOR: internal fun A.ext(): kotlin.Unit defined in root package
+// PARAM_TYPES: B
+fun main(args: Array<String>) {
+    val a: A = B()
+    a.ext()
+}
+
+fun A.ext() {
+    if (this !is B) return
+    val b = <selection>foo()</selection>
+}
+
+open class A
+class B: A() {
+    fun foo() = 1
+}