FIR2IR: use lookupTag or class to getLocalClass, not classId

Before this commit, we sometimes tried to fetch anonymous object by id,
getting sometimes a wrong result because it's singleton.
Now we use lookupTag or FIR class itself instead.

#KT-44050 Fixed

compiler/testData/codegen/box/objects/useAnonymousObjectFunction.kt

@@ -0,0 +1,46 @@
+// KT-44050
+
+enum class Enum {
+    Entry1() {
+        fun bogus() = 42
+    },
+    Entry2() {
+        fun bogus() = 42
+    }
+}
+
+class Outer {
+    fun barCaller(): Enum = obj1.bar()
+    fun bazCaller(): Enum = obj2.baz()
+
+    private abstract inner class Inner<T>(val default: T) {
+        abstract fun foo()
+    }
+
+    private val obj1 = object : Inner<Enum>(Enum.Entry1) {
+        override fun foo() {
+            TODO("not related")
+        }
+
+        fun bar(): Enum {
+            return default
+        }
+    }
+
+    private val obj2 = object : Inner<Enum>(Enum.Entry2) {
+        override fun foo() {
+            TODO("not related")
+        }
+
+        fun baz(): Enum {
+            return default
+        }
+    }
+}
+
+fun box(): String {
+    val o = Outer()
+    if (o.barCaller() != Enum.Entry1) return "Fail1"
+    if (o.bazCaller() != Enum.Entry2) return "Fail2"
+    return "OK"
+}