Diagnostics for incorrect enum members order, when enum entry follows enum member. A few diagnostic tests.

Now incorrect enum members order is treated as a warning.

compiler/testData/diagnostics/tests/enum/enumMixedWithCommas.kt

@@ -0,0 +1,9 @@
+enum class MixedEnum {
+    <!ENUM_ENTRY_USES_DEPRECATED_OR_NO_DELIMITER!>ENTRY1<!>,
+    companion object {
+        val first = 1
+    }
+    <!ENUM_ENTRY_USES_DEPRECATED_OR_NO_DELIMITER, ENUM_ENTRY_AFTER_ENUM_MEMBER!>ENTRY2<!>,
+    fun foo(): String = "xyz"
+    <!ENUM_ENTRY_AFTER_ENUM_MEMBER!>ENTRY3<!>
+}