JVM_IR: defer some branch optimizations to codegen.

Specifically, defer the removal of hand-written "if (true|false)" from
JvmBuiltinOptimizationLowering into codegen so that appropriate debug
info (and a NOP) can be inserted.

Change-Id: Ia11af05ad8b4251946bd3e685fb7c3319f0f433f

compiler/testData/codegen/bytecodeText/controlStructures/ifConsts.kt

@@ -0,0 +1,19 @@
+fun foo(b: Boolean): Int {
+    return if (b) {
+        100
+    } else if (false) {
+        101
+    } else if (true) {
+        102
+    } else if (true) {
+        103
+    } else if (b) {
+        104
+    } else {
+        105
+    }
+}
+
+// 2 BIPUSH
+// 1 BIPUSH 100
+// 1 BIPUSH 102