Better main function recognition and tests

fix vararg main

idea/testData/run/MainInTest/module/src/mainInPackageVarianceOut.kt

@@ -1,5 +1,5 @@
 package pkg5
 
 fun main(args: Array<out String>) {
-    // no
+    // yes
 }

idea/testData/run/MainInTest/module/src/varargMain.kt

@@ -0,0 +1,5 @@
+package varargMain
+
+fun main(vararg args: String) {
+    // yes
+}