Allow top-level type aliases in scripts

compiler/testData/diagnostics/tests/script/typealiasInScript.kts

@@ -0,0 +1,9 @@
+typealias TopLevelInScript = String
+
+class C {
+    <!TOPLEVEL_TYPEALIASES_ONLY!>typealias NestedInClass = String<!>
+}
+
+fun foo() {
+    <!TOPLEVEL_TYPEALIASES_ONLY!>typealias Local = String<!>
+}

compiler/testData/diagnostics/tests/script/typealiasInScript.txt

@@ -0,0 +1,19 @@
+package
+
+public final class TypealiasInScript : kotlin.script.templates.standard.ScriptTemplateWithArgs {
+    public constructor TypealiasInScript(/*0*/ args: kotlin.Array<kotlin.String>)
+    public final override /*1*/ /*fake_override*/ val args: kotlin.Array<kotlin.String>
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public final class C {
+        public constructor C()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        public typealias NestedInClass = kotlin.String
+    }
+    public typealias TopLevelInScript = kotlin.String
+}