[api-minor] Implement basic support for OptionalContent Usage dicts (issue 5764, bug 1826783)

The following are some highlights of this patch:
 - In the Worker we only extract a *subset* of the potential contents of the `Usage` dictionary, to avoid having to implement/test a bunch of code that'd be completely unused in the viewer.

 - In order to still allow the user to *manually* override the default visible layers in the viewer, the viewable/printable state is purposely *not* enforced during initialization in the `OptionalContentConfig` constructor.

 - Printing will now always use the *default* visible layers, rather than using the same state as the viewer (as was the case previously).
   This ensures that the printing-output will correctly take the `Usage` dictionary into account, and in practice toggling of visible layers rarely seem to be necessary except in the viewer itself (if at all).[1]

---
[1] In the unlikely case that it'd ever be deemed necessary to support fine-grained control of optional content visibility during printing, some new (additional) UI would likely be needed to support that case.

web/firefox_print_service.js

@@ -119,15 +119,15 @@ class FirefoxPrintService {
     pagesOverview,
     printContainer,
     printResolution,
-    optionalContentConfigPromise = null,
     printAnnotationStoragePromise = null,
   }) {
     this.pdfDocument = pdfDocument;
     this.pagesOverview = pagesOverview;
     this.printContainer = printContainer;
     this._printResolution = printResolution || 150;
-    this._optionalContentConfigPromise =
-      optionalContentConfigPromise || pdfDocument.getOptionalContentConfig();
+    this._optionalContentConfigPromise = pdfDocument.getOptionalContentConfig({
+      intent: "print",
+    });
     this._printAnnotationStoragePromise =
       printAnnotationStoragePromise || Promise.resolve();
   }