Add support for parsing raw events using custom transform in PushInputAdapter

[arhamchopra]

Summary

• Add a transformRawEvent virtual hook to PushInputAdapter that allows subclasses to apply arbitrary transformations to pushed events on the engine thread before they are consumed by the csp engine.
• Change consumeEvent return type from bool to PushEvent * (nullptr = consumed, non-null = defer to next cycle) and add a reconsuming flag to skip transformation on events already transformed in a prior pass.
• This enables push adapters to push raw payloads from the adapter thread and have them transformed into final tick values on the engine thread — useful when the transformation requires engine-thread state, deferred evaluation, type conversion, or arbitrary C++ logic.
• Add a test C++ adapter (CallablePyPushInputAdapter) and Python tests demonstrating the feature, including reconsume correctness for both ungrouped and grouped adapters.

Design

A new transformEvents flag on PushInputAdapter (set via constructor) routes events through a single virtual hook in consumeEvent:

• transformRawEvent(PushEvent * raw_event) — transform the pushed event into a new parsed event for the engine. The subclass implementation must:
  • Delete the original raw event
  • Preserve event properties (e.g. isGroupEnd flag) on the new event

The transform runs before the group LOCKED check in consumeEvent, so events stored in PendingPushEvents are always already-transformed. On reconsuming (second pass), consumeEvent receives reconsuming=true and skips transformRawEvent to avoid double-transformation.

Return value of consumeEvent changed from bool to PushEvent *:

• nullptr — event was consumed
• Non-null — event was not consumed (e.g. group LOCKED, ungrouped NC already ticked this cycle); returned event is added to PendingPushEvents for the next engine cycle

[robambalu]

gtg if you want to remove it from draft