CLDR-14913 Add Download XML button to Survey Tool

-Front end: new GenerateVxml.vue, cldrGenerateVxml.mjs

-Back end: new GenerateVxml.java, VxmlQueue.java, VxmlGenerator.java

-Run the task in its own thread, with multiple http requests fetching status until done

-Partly imitate implementation of Priority Items Summary: GenerateVxml.java corresponds to Summary.java; VxmlGenerator.java corresponds to VettingViewer.java; VxmlQueue.java corresponds to VettingViewerQueue.java

-Revise OutputFileManager.java as needed and also to fix some (not all) compiler warnings

-Disable Announce requests while VXML generation is in progress (only on front end; only affects the browser of the Admin user, not other users if running on remote server)

-Remove common/annotations/ff.xml at least temporarily; it is essentially empty and leads to verification failure: present in baseline but not in vxml

-Fix bug in XPathTable.loadXPaths, DB connection without commit, change getDBConnection to getAConnection for auto-commit (pre-existing bug was especially problematic throwing exception when generating VXML)

-Improve debugging feature in DBUtils.java slightly and add comment about remaining imperfection

-Use auto-commit in STFactory.setupDB and make the related boolean dbIsSetup private

-Remove dead code

-Comments

tools/cldr-apps/src/main/java/org/unicode/cldr/web/VxmlQueue.java

@@ -292,9 +292,7 @@ private QueueEntry getEntry(QueueMemberId qmi) {
         return entry;
     }
 
-    /**
-     * Estimated percentage complete for VXML generation
-     */
+    /** Estimated percentage complete for VXML generation */
     private int percent = 0;
 
     private void setPercent(int p) {