Provide an indexation progress bar and message

Right now when navigating to http://localhost:8080/xwiki/bin/admin/XWiki/XWikiPreferences?editor=globaladmin&section=XWiki.Extension.Security.Code.Admin after having started XWiki , the LD is empty and there's a strange message: Could not find any previous indexation processing.

As a user, I couldn't understand what this message meant and I couldn't know if the indexation had been done or not. Actually I understood the message as something that went wrong.

I had to read https://extensions.xwiki.org/xwiki/bin/view/Extension/Extension/Security/Index/#HScheduling to understand how it works.

It would improve the UX a lot if there was an indexation progress bar with some information, basically:

• Knowing if the Extension indexation is in progress and the progress level
• Knowing about the Security indexation level
• Display some message about when it was last indexed, similar to the extension index: "Indexed on 2023/08/04 15:03. Any modification made after that to a remote extension won't appear."

Thanks