Add a getDocId method to the idFactory, in Page instances, to avoid passing around PDFManager instances unnecessarily (PR 7941 follow-up)

This way we can avoid manually building a "document id" in multiple places in `evaluator.js`, and it also let's us avoid passing in an otherwise unnecessary `PDFManager` instance when creating a `PartialEvaluator`.

src/core/annotation.js

@@ -50,7 +50,7 @@ class AnnotationFactory {
     if (!isDict(dict)) {
       return;
     }
-    let id = isRef(ref) ? ref.toString() : 'annot_' + idFactory.createObjId();
+    let id = isRef(ref) ? ref.toString() : `annot_${idFactory.createObjId()}`;
 
     // Determine the annotation's subtype.
     let subtype = dict.get('Subtype');