[api-minor] Add support for OpenAction destinations (issue 10332)

Note that the OpenAction dictionary may contain other information besides just a destination array, e.g. instructions for auto-printing[1].
Given first of all that an arbitrary `Dict` cannot be sent from the Worker (since cloning would fail), and second of all that the data obviously needs to be validated, this patch purposely only adds support for fetching a destination from the OpenAction entry[2].

---
[1] This information is, currently in PDF.js, being included through the `getJavaScript` API method.

[2] This significantly reduces the complexity of the implementation, which seems fine for now. If there's ever need for other kinds of OpenAction to be fetched, additional API methods could/should be implemented as necessary (could e.g. follow the `getOpenActionWhatever` naming scheme).

src/core/obj.js

@@ -392,6 +392,28 @@ class Catalog {
     return shadow(this, 'pageMode', pageMode);
   }
 
+  get openActionDestination() {
+    const obj = this.catDict.get('OpenAction');
+    let openActionDest = null;
+
+    if (isDict(obj)) {
+      // Convert the OpenAction dictionary into a format that works with
+      // `parseDestDictionary`, to avoid having to re-implement those checks.
+      const destDict = new Dict(this.xref);
+      destDict.set('A', obj);
+
+      const resultObj = { url: null, dest: null, };
+      Catalog.parseDestDictionary({ destDict, resultObj, });
+
+      if (Array.isArray(resultObj.dest)) {
+        openActionDest = resultObj.dest;
+      }
+    } else if (Array.isArray(obj)) {
+      openActionDest = obj;
+    }
+    return shadow(this, 'openActionDestination', openActionDest);
+  }
+
   get attachments() {
     const obj = this.catDict.get('Names');
     let attachments = null;

src/core/worker.js

@@ -531,6 +531,10 @@ var WorkerMessageHandler = {
       return pdfManager.ensureCatalog('pageMode');
     });
 
+    handler.on('getOpenActionDestination', function(data) {
+      return pdfManager.ensureCatalog('openActionDestination');
+    });
+
     handler.on('GetAttachments',
       function wphSetupGetAttachments(data) {
         return pdfManager.ensureCatalog('attachments');