[FIR] Support smartcast after reference equality check

#KT-39000 Fixed

compiler/fir/analysis-tests/testData/resolve/smartcasts/kt39000.kt

@@ -0,0 +1,12 @@
+interface A
+class B: A
+
+val X = B()
+
+fun foo(b: B) {}
+
+fun main(a: A) {
+    if (a === X) {
+        foo(a)
+    }
+}

compiler/fir/analysis-tests/testData/resolve/smartcasts/kt39000.txt

@@ -0,0 +1,21 @@
+FILE: kt39000.kt
+    public abstract interface A : R|kotlin/Any| {
+    }
+    public final class B : R|A| {
+        public constructor(): R|B| {
+            super<R|kotlin/Any|>()
+        }
+
+    }
+    public final val X: R|B| = R|/B.B|()
+        public get(): R|B|
+    public final fun foo(b: R|B|): R|kotlin/Unit| {
+    }
+    public final fun main(a: R|A|): R|kotlin/Unit| {
+        when () {
+            ===(R|<local>/a|, R|/X|) ->  {
+                R|/foo|(R|<local>/a|)
+            }
+        }
+
+    }