Remove jmx beans

[Arnei]

Fixes #6705.

These beans seem to go unused and there are performance concerns surrounding the jmx statistics. Therefore this patch removes all jmx beans, to make our code a little bit simpler.

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[gregorydlogan]

@lkiesow I have the vaguest recollection that you argued against removing JMX beans previously, am I right?
@rute-santos Is this relevant to your site?

[mtneug]

JMX for OC job statistics can still be a performance issue during startup [1]. So +1 to remove JMX at least for that part.

[1] While it is possible to set the job statistic aggregation to only consider 1 day, the default is still 14. IIRC JMX is initialized before the config is read, i.e. even if 1 day is configured, during startup the default of 14 still applies. This will delay the whole startup of Opencast potentially waiting for a very long query. I don't think it is worth doing that given that JMX isn't used by (most/all?) adopters.

[JamesUoM]

+1 for me, JMX statistics has never been anything but a performance issue.

[gregorydlogan]

Considering there's always (that person)[https://xkcd.com/1172/] out there somewhere, this should have a release notes entry too.