Make HstComponent instances *unshared* between different requests

In CMS-13523, commit c7ffe78 , we introduced that XPages do not share their HstComponent instances with other requests: The instances are not registered in the component registry at all.

This means that those HstComponent instances do not have to take concurrency into account, and can just store/change instance variables during a request

To keep it in sync, we can better also get rid of the HstComponent registry for HstComponent instances resulting from hst config as well. The performance penalty is extremely minimal, unless the HstComponent has an expensive #init method which I have not seen in the last 12 years.

After this, HstComponent instances do not have to be treated thread safe any more but are just flyweight objects PER request and GC-ed at the end