[FIR] Unwrap smartcast on dispatch receiver in CFA for class initialization

^KT-56863 Fixed

compiler/fir/analysis-tests/testData/resolve/cfa/smartcastOnThisDuringClassInitialization.fir.txt

@@ -0,0 +1,17 @@
+FILE: smartcastOnThisDuringClassInitialization.kt
+    public abstract interface I : R|kotlin/Any| {
+    }
+    public open class Some : R|kotlin/Any| {
+        public constructor(): R|Some| {
+            super<R|kotlin/Any|>()
+        }
+
+        public final val x: R|kotlin/Int|
+            public get(): R|kotlin/Int|
+
+        init {
+            (this@R|/Some| as R|I|)
+            this@R|/Some|.R|/Some.x| = Int(1)
+        }
+
+    }

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

@@ -0,0 +1,11 @@
+// ISSUE: KT-56863
+interface I
+
+open class Some {
+    val x: Int
+
+    init {
+        this as I
+        x = 1
+    }
+}