Test experimental coroutines version requirement on JVM only

Modify 'suspendFun' and 'nestedClassMembers' tests so that pre-release
suspend functions are tested only on JVM, where they are still supported.

compiler/testData/versionRequirement/suspendFun_1_2.kt

@@ -0,0 +1,16 @@
+package test
+
+suspend fun topLevel() {}
+
+class Foo {
+    constructor(block: suspend () -> Unit)
+
+    suspend fun member() {}
+}
+
+fun async1(block: suspend () -> Unit) {}
+fun (suspend () -> Unit).async2() {}
+fun async3(): suspend () -> Unit = null!!
+fun async4(): Map<Int, suspend () -> Unit>? = null
+
+val (suspend () -> Unit).asyncVal: () -> Unit get() = {}