Introduce minByOrNull and maxByOrNull extension functions #KT-38854

compiler/testData/codegen/bytecodeText/boxingOptimization/maxMinByOrNull.kt

@@ -0,0 +1,51 @@
+// FILE: list.kt
+
+val intList = listOf(1, 2, 3)
+val longList = listOf(1L, 2L, 3L)
+
+// FILE: box.kt
+
+fun box(): String {
+    val intListMin = intList.minByOrNull { it } ?: -1
+    if (intListMin != 1) return "Fail intListMin=$intListMin"
+
+    val intListMax = intList.maxByOrNull { it } ?: -1
+    if (intListMax != 3) return "Fail intListMax=$intListMax"
+
+    val longListMin = longList.minByOrNull { it } ?: -1
+    if (longListMin != 1L) return "Fail longListMin=$longListMin"
+
+    val longListMax = longList.maxByOrNull { it } ?: -1
+    if (longListMax != 3L) return "Fail longListMax=$longListMax"
+
+    return "OK"
+}
+
+// @BoxKt.class:
+// -- no compareTo
+// 0 compareTo
+// -- comparisons are properly fused with conditional jumps
+// comparisons: 0 + fake inline variables: 12
+// 12 ICONST_0
+// 1 IF_ICMPGE
+// 1 IF_ICMPLE
+// 4 LCMP
+// 1 IFGE
+// 1 IFLE
+
+// JVM_TEMPLATES
+// -- no boxing but lots of StringBuilder calls
+// 0 valueOf
+// 0 Intrinsics.stringPlus
+// 4 StringBuilder.<init>
+// 8 StringBuilder.append
+// 4 StringBuilder.toString
+
+// JVM_IR_TEMPLATES
+// -- perform boxing and call Intrinsics.stringPlus instead
+// -- of having inlined string builder allocation, appends, and toString
+// 4 valueOf
+// 4 Intrinsics.stringPlus
+// 0 StringBuilder.<init>
+// 0 StringBuilder.append
+// 0 StringBuilder.toString