Add Sentry support for Issues and Performance

[dwd]

I've been working on this for a few weeks, and it'll take a lot more work, but I thought it was worth opening a Draft PR for visibility.

Note that this is utterly useless with Sentry-SaaS unless you have deep pockets - I'm running it for my server against a self-hosted Sentry - but I'm generating a transaction per stanza, currently, as well as for S2S connections and more.

[guusdk]

My immediate concern is that we're adding an awful lot of very specific code right into pretty core code, to facilitate a very specific, proprietary API. Is there any way to make this a lot less invasive, from a code perspective? Move things to a plugin, or at least a set of dedicated classes, for example by introducing generic interfaces, that then can be used by more specific code)?

It's nice to see something like this materialize though. Back in the day, we created a much less versatile solution that shot things straight into JIRA. That was surprisingly crude but effective.