[JVM IR] Support Suspend Main

This adds supports for (parameterless) suspend main entry points for
the JVM IR backend.

In case main is a suspend function, it gains a continuation during
lowering, so we simply generate a plain old `public static void
main(String[] args)`. This entry point invokes `suspend main` via
`kotlin.coroutines.jvm.internal.RunSuspendKt#runSuspend`.

This PR introduces `runSuspend` as a built-in, and generates the
following `main`, passing `args` as appropriate:

```
fun main(args: Array<String>) {
  runSuspend { main(args) }
}
```

The phase ordering has been reshuffled countrary to previous
discussion on #2780, as the MainMethodGeneration pass now introduces lambdas in
the IR. Hence, it has to run before InventNamesForLocalClasses, yet
still after JvmOverloadsAnnotations.

Some dead code was discovered in AddContinuationLowering

compiler/testData/writeSignature/suspendMain/parameterlessSuspendMain.kt

@@ -0,0 +1,12 @@
+// WITH_RUNTIME
+suspend fun main() {
+
+}
+
+// method: ParameterlessSuspendMainKt::main
+// jvm signature:     (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+// generic signature: (Lkotlin/coroutines/Continuation<-Lkotlin/Unit;>;)Ljava/lang/Object;
+
+// method: ParameterlessSuspendMainKt::main
+// jvm signature:     ([Ljava/lang/String;)V
+// generic signature: null