Require event definition for Internal events

Problem

Event definitions are not required for Internal Events. This leads to a lack of documentation for newly instrumented events, as well as the problem that it makes it impossible to create further validations around internal events, like making sure that the event name stays unique or reusing the event through the generator

Desired Outcome

• Adding a new internal event without an appropriate internal event definition is impossible.
• All already instrumented Internal events have an event definition
• The generator is changed to be able to reuse an existing event instead of creating one if one with the same name already exists

Proposed Solution

TBD

How to verify

Try to create an MR with a newly instrumented internal event. It should fail.