[FIR2IR] Properly insert implicit casts to extension receiver in case of intersection smartcast type

^KT-62863 Fixed

compiler/testData/ir/irText/expressions/genericReceiverOnExtensionWithSmartcast.kt.txt

@@ -0,0 +1,18 @@
+fun <F : CharSequence> F.bar() {
+}
+
+inline fun <reified T : CharSequence> test_1(x: Any) {
+  when {
+    x is T -> { // BLOCK
+      x /*as T */.bar<T>()
+    }
+  }
+}
+
+fun test_2(x: Any?) {
+  when {
+    x is CharSequence -> { // BLOCK
+      x /*as CharSequence */.bar<CharSequence>()
+    }
+  }
+}