Fix hang during rename-and-move in Zotero 6 (#594)

Resulting in not all annotations being transferred and the old
attachment not being deleted

Regression after zotero/zotero@734057ff9b, which added a transaction
requirement to `Zotero.Items.moveChildItems()` but tried to preserve
backwards compatibility with ZotFile. Unfortunately it had a bug, and a
race condition with another transacation during the process results in a
hang anyway if `moveChildItems()` isn't called in a transaction, so just
change ZotFile to follow the new requirement.

This also fixes `saveTx()` being called without an await.

Fixes #593

chrome/content/zotfile/zotfile.js

@@ -911,18 +911,21 @@ Zotero.ZotFile = new function() {
                 win.ZoteroPane.itemsView.selectItems(selection);
             }
             // update links to attachment file in notes
-            Zotero.Items.get(item.getNotes()).forEach(note => {
+            var notes = Zotero.Items.get(item.getNotes());
+            for (let note of notes) {
                 var content = note.getNote();
                 content = content.replace(new RegExp('open-pdf/([\\w\\W\\d]{1,10})_' + att.key, 'g'), 'open-pdf/$1_' + attNew.key);
                 note.setNote(content);
-                note.saveTx();
-            });
+                yield note.saveTx();
+            }
             // transfer various attachment data
             //
             // should stay in sync with Zotero.Attachments.convertLinkedFileToStoredFile()
             if (this.isZotero6OrLater) {
                 // move child annotations and embedded-image attachments
-                yield Zotero.Items.moveChildItems(att, attNew);
+                yield Zotero.DB.executeTransaction(async function () {
+                    await Zotero.Items.moveChildItems(att, attNew);
+                });
                 // copy relations pointing to the old item
                 yield Zotero.Relations.copyObjectSubjectRelations(att, attNew);
                 // transfer full-text item index
@@ -975,18 +978,21 @@ Zotero.ZotFile = new function() {
                 win.ZoteroPane.itemsView.selectItems(selection);
             }
             // update links to attachment file in notes
-            Zotero.Items.get(item.getNotes()).forEach(note => {
+            var notes = Zotero.Items.get(item.getNotes());
+            for (let note of notes) {
                 var content = note.getNote();
                 content = content.replace(new RegExp('open-pdf/([\\w\\W\\d]{1,10})_' + att.key, 'g'), 'open-pdf/$1_' + attNew.key);
                 note.setNote(content);
-                note.saveTx();
-            });
+                yield note.saveTx();
+            }
             // transfer various attachment data
             //
             // should stay in sync with Zotero.Attachments.convertLinkedFileToStoredFile()
             if (this.isZotero6OrLater) {
                 // move child annotations and embedded-image attachments
-                yield Zotero.Items.moveChildItems(att, attNew);
+                yield Zotero.DB.executeTransaction(async function () {
+                    await Zotero.Items.moveChildItems(att, attNew);
+                });
                 // copy relations pointing to the old item
                 yield Zotero.Relations.copyObjectSubjectRelations(att, attNew);
                 // transfer full-text item index