JVM_IR KT-42010 use IINC for postfix int increment/decrement

compiler/testData/codegen/bytecodeText/intrinsics/postfixIncrDecr.kt

@@ -0,0 +1,34 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+
+fun use(i: Int) {}
+
+fun testPostfixIncr0() {
+    var k = 0
+    k++
+    use(k)
+}
+
+fun testPostfixIncr1() {
+    var k = 0
+    val t = k++
+    use(k)
+    use(t)
+}
+
+fun testPostfixDecr0() {
+    var k = 0
+    k--
+    use(k)
+}
+
+fun testPostfixDecr1() {
+    var k = 0
+    val t = k--
+    use(k)
+    use(t)
+}
+
+// 6 ISTORE
+// 8 ILOAD
+// 0 ICONST_1
+// 4 IINC