infocentre needs a sitemap and to stop mangling root based on user agent

At the moment infocentre is using the user agent to provide different contents to the client depending on whether it is a bot or not. See the following helpdesk issues which are side effects of this:

- https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/2298
- https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/2160
- https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/2326

The bad google search results may be the result of perceived bad behaviour like [cloaking](https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/2326) or simply not having the links visible to crawl.

Either way, we can now remove the workarounds added in le in [this commit](https://github.com/eclipse-platform/eclipse.platform.ua/commit/f983223ddbc34a4df62e0fee0de82b2f86b7a5cb) for [bug 69055](https://bugs.eclipse.org/69055) as there is more modern ways to do it.

From @laeubi's comment [in gitlab](https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/2298#note_1047809):

> I already mentioned it in the other topic, "todays" preferred technology (for more than 10+ year probably) it having a site-map instead (and that's what this html page actually is):
>
> * https://www.sitemaps.org/index.html
> * https://www.sitemaps.org/protocol.html
> * https://www.sitemaps.org/faq.html#faq_sitemap_location
> * https://developers.google.com/search/docs/crawling-indexing/robots/create-robots-txt (see `Sitemap` directive)

AFAICT the root method that changes the rendering is isBot:

https://github.com/eclipse-platform/eclipse.platform.ua/blob/8c012ce5d060b9efa08702d07acbd32b5014fc3c/org.eclipse.help.webapp/src/org/eclipse/help/internal/webapp/data/UrlUtil.java#L263-L271