[JVM_IR]: Improve stepping for when.

Additionally, use the line number of the class for default interface
dispatch methods.

compiler/testData/debug/stepping/whenSubject2.kt

@@ -0,0 +1,121 @@
+// FILE: test.kt
+
+fun foo(x: Int) {
+    when
+        (x)
+    {
+        21 -> foo(42)
+        42 -> foo(63)
+        else -> 1
+    }
+
+    val t = when
+        (x)
+    {
+        21 -> foo(42)
+        42 -> foo(63)
+        else -> 2
+    }
+}
+
+fun box() {
+    foo(21)
+}
+
+// JVM_IR uses the line number of the when for the table switch and therefore,
+// it stops on the subject line first, then on the when line (line 4 and 12), and
+// then goes to the right branch.
+
+// LINENUMBERS
+// test.kt:22 box
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:7 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:8 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:9 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:17 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:8 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:16 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:9 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:17 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:16 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:7 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:15 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:8 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:9 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:17 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:8 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:16 foo
+// test.kt:5 foo
+// LINENUMBERS JVM_IR
+// test.kt:4 foo
+// LINENUMBERS
+// test.kt:9 foo
+// test.kt:13 foo
+// LINENUMBERS JVM_IR
+// test.kt:12 foo
+// LINENUMBERS
+// test.kt:17 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:16 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:15 foo
+// test.kt:12 foo
+// test.kt:19 foo
+// test.kt:23 box