Export registered events/messages to file

This has come up during the EtherLab Messaging meeting in March 2025.

Since PdServ 'knows' the registered messages/events, it should be able to export a list of messages that helps maintaining message translations. This file should be exported either

• on demand via a function call pdserv_export_events(pdserv, path)
• or in pdserv_prepare() context to a path set in the configuration file (not by default).

The format of the message list file was considered to be a text file with two columns:

• Path
• Vector size

The severity/priority can not be exported, because it is only set during event triggering.

Maybe it would be nice to make the exported file a YAML document to also export the text array, but since the actual texts are to be defined in the messages.xml, this will not help much.