Elide import namespace from which only const enums are used (#20320)

tests/cases/compiler/constEnumNamespaceReferenceCausesNoImport.ts

@@ -0,0 +1,16 @@
+// @filename: foo.ts
+export const enum ConstFooEnum {
+    Some,
+    Values,
+    Here
+};
+export function fooFunc(): void { /* removed */ }
+// @filename: index.ts
+import * as Foo from "./foo";
+
+function check(x: Foo.ConstFooEnum): void {
+  switch (x) {
+    case Foo.ConstFooEnum.Some:
+      break;
+  }
+}