Speed up eventy event firing

[OttoWinter]

Freescout appears to use Eventy to allow modules to customize certain aspects of freescout, for example the user getFullName:

https://github.com/freescout-helpdesk/freescout/blob/40fc84546168c7fed1eacf55759ff008371815f4/app/User.php#L216

Unfortunately, this eventy library appears to be quite inefficient, especially when you have large amounts of listeners (it does a O(n) search through all listeners globally to find matching ones, plus each time does a O(n log n) sort by priority).

For example, on an instance I was profiling, there were ~120 listeners, thus making a single (!) User::getFullName take a whopping 3ms (with ~100 getFullName calls for listing assignable users this has a major impact; and that's just for the getFullName calls).

This PR overrides Eventy, to replace its internal data structure to be more efficient (keyed by the hook).

In total, this reduced mailbox loading times for my organization from ~1.5s to ~0.5s.

Note: I barely know PHP (in fact most of this code was generated by Copilot), so the code probably is very bad ^^ If there's something that can be done better let me know.

Also note that technically I'm changing the (public) getListeners function argument types here. This method only appears to be used inside Eventy, but this could still cause problems (it works on my instance though).

[freescout-helpdesk]

Thanks. Very good improvement. Your code is good.

For us page load speed improved by an average of about 30%.

[raramuridesign]

@OttoWinter Thank you for this, it has improved our installations
M.