Reuse type nodes from optional parameters even when not written as a union with undefined (#48605)

* Reuse type nodes from optional parameters and properties even when not written as a union with `undefined`

* Remove newly unneeded NodeBuilderFlag

* Update public API

* Update baselines from main

tests/cases/conformance/declarationEmit/leaveOptionalParameterAsWritten.ts

@@ -0,0 +1,22 @@
+// @module: esnext
+// @outDir: dist
+// @declaration: true
+// @emitDeclarationOnly: true
+// @strictNullChecks: true
+
+// @Filename: a.ts
+export interface Foo {}
+
+// @Filename: b.ts
+import * as a from "./a";
+declare global {
+  namespace teams {
+    export namespace calling {
+      export import Foo = a.Foo;
+    }
+  }
+}
+
+// @Filename: c.ts
+type Foo = teams.calling.Foo;
+export const bar = (p?: Foo) => {}