Don't create NamespaceType for enum entries

Enum entry expressions have the type of their enum, so it shouldn't be possible
to access static nested classes of enum entries from outside.

This fixes BlackBoxCodegenTestGenerated$CallableReference.testEnumNameMethod

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

@@ -0,0 +1,14 @@
+enum class E {
+    FIRST
+    SECOND {
+        class A
+    }
+}
+
+val foo: Any.() -> Unit = {}
+
+fun f1() = E.FIRST.foo()
+fun f2() = E.FIRST.(foo)()
+fun f3() = E.SECOND.foo()
+fun f4() = E.SECOND.(foo)()
+fun f5() = E.SECOND.<!UNRESOLVED_REFERENCE!>A<!>()