fix: remove action feature flag and include execution (#9727)

# Which Problems Are Solved

Actions v2 is not a feature flag anymore, include functionality on
executions is not used and json tags of proto messages are handled
incorrectly.

# How the Problems Are Solved

- Remove actions from the feature flags on system and instance level
- Remove include type on executions, only in the API, later maybe in the
handling logic as well
- Use protojson in request and response handling of actions v2

# Additional Changes

- Correct integration tests for request and response handling
- Use json.RawMessage for events, so that the event payload is not
base64 encoded
- Added separate context for async webhook calls, that executions are
not cancelled when called async

# Additional Context

Related to #9759 
Closes #9710

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/query/projection/system_features.go

@@ -72,10 +72,6 @@ func (*systemFeatureProjection) Reducers() []handler.AggregateReducer {
 				Event:  feature_v2.SystemTokenExchangeEventType,
 				Reduce: reduceSystemSetFeature[bool],
 			},
-			{
-				Event:  feature_v2.SystemActionsEventType,
-				Reduce: reduceSystemSetFeature[bool],
-			},
 			{
 				Event:  feature_v2.SystemImprovedPerformanceEventType,
 				Reduce: reduceSystemSetFeature[[]feature.ImprovedPerformanceType],