[IR] Support user-defined equals for MFVC

Signed-off-by: Evgeniy.Zhelenskiy <Evgeniy.Zhelenskiy@jetbrains.com>

#KT-1179

compiler/testData/diagnostics/tests/valueClasses/inefficientEqualsOverridingInMfvc.kt

@@ -0,0 +1,28 @@
+// FIR_IDENTICAL
+// WITH_STDLIB
+// !DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
+// LANGUAGE: +CustomEqualsInValueClasses +ValueClasses
+
+@JvmInline
+value class MFVC1(val x: Int, val y: Int) {
+    override fun <!INEFFICIENT_EQUALS_OVERRIDING_IN_VALUE_CLASS!>equals<!>(other: Any?): Boolean {
+        if (other !is MFVC1) {
+            return false
+        }
+        return x == other.x
+    }
+}
+
+@JvmInline
+value class MFVC2(val x: Int, val y: Int) {
+    override fun hashCode() = 0
+}
+
+@JvmInline
+value class MFVC3(val x: Int, val y: Int) {
+    override fun equals(other: Any?) = true
+
+    fun equals(other: MFVC3) = true
+
+    override fun hashCode() = 0
+}