Enum entries: add new tests with language feature ON & fix checker

compiler/testData/diagnostics/tests/enum/entries/entriesPropertyImportedClashOn.fir.kt

@@ -0,0 +1,22 @@
+// !LANGUAGE: +EnumEntries
+// WITH_STDLIB
+
+package foo
+
+import foo.A.Companion.entries
+
+enum class A {
+    ;
+
+    companion object {
+        val entries = 0
+    }
+}
+
+fun test() {
+    A.<!OPT_IN_USAGE_ERROR!>entries<!>
+
+    with(A) {
+        entries
+    }
+}