[BUGFIX] Support union types for event listeners

Since #94345 it's possible to omit the "event"
identifier when configuring an event listener,
since the service can be resolved using reflection.
This however did until now not work when using
union types. This patch therefore adjusts the
corresponding compiler pass, making it possible
to use the same method for listing on multiple
events.

Resolves: #101264
Related: #94345
Releases: main, 12.4
Change-Id: I5668269104515811d3c916c832942ef532bdfa27
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79821


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>