Use class.name for Internal events category value in Backend

Problem

Root problem described in &12242 (closed).

We're currently not passing any information about where in the codebase was a backend event was triggered. Allowing devs to pass that information but making it a manual process is error prone and requires additional work, which goes against the aim of internal events to make instrumentation easier. At the same time, it was encouraged to pass self.class.name in the category field of a backend Snowplow event.

Without passing the same information we're essentially loosing valuable information and create a hurdle for migrating to Internal Events (see &12242 (comment 1692898773)).

Desired Outcome

class.name of the class that's calling InternalEvents.trackEvent is sent in the category field to Snowplow.

Proposed Solution

TBD

How to verify

Check whether category field is filled correctly for incoming Snowplow events for an Internal Event in common_mart.mart_behavior_structured_event