[JVM_IR] Generate line numbers and nops for init blocks.

This seems to be what JVM does and it allows you to set a
breakpoint on the init line.

compiler/testData/debug/stepping/initBlocks.kt

@@ -51,10 +51,8 @@ fun box() {
     Zoo()
 }
 
-// IGNORE_BACKEND: JVM_IR
-// The JVM_IR does not generate code that will break on the line
-// containing the `init`, nor the exit from the `init`. It only
-// contains lines for the contents of the init blocks.
+// JVM_IR has an extra step back to the line of the class
+// declaration for the return in the constructor.
 
 // LINENUMBERS
 // test.kt:48 box
@@ -64,6 +62,9 @@ fun box() {
 // test.kt:45 x
 // test.kt:7 <init>
 // test.kt:8 <init>
+// LINENUMBERS JVM_IR
+// test.kt:3 <init>
+// LINENUMBERS
 // test.kt:48 box
 // test.kt:49 box
 // test.kt:11 <init>
@@ -73,6 +74,9 @@ fun box() {
 // test.kt:16 <init>
 // test.kt:17 <init>
 // test.kt:18 <init>
+// LINENUMBERS JVM_IR
+// test.kt:11 <init>
+// LINENUMBERS
 // test.kt:49 box
 // test.kt:50 box
 // test.kt:21 <init>
@@ -85,6 +89,9 @@ fun box() {
 // test.kt:28 <init>
 // test.kt:29 <init>
 // test.kt:30 <init>
+// LINENUMBERS JVM_IR
+// test.kt:21 <init>
+// LINENUMBERS
 // test.kt:50 box
 // test.kt:51 box
 // test.kt:33 <init>
@@ -94,5 +101,8 @@ fun box() {
 // test.kt:39 <init>
 // test.kt:40 <init>
 // test.kt:42 <init>
+// LINENUMBERS JVM_IR
+// test.kt:33 <init>
+// LINENUMBERS
 // test.kt:51 box
 // test.kt:52 box