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/system_features.go

@@ -25,7 +25,6 @@ type SystemFeatures struct {
 	LegacyIntrospection             FeatureSource[bool]
 	UserSchema                      FeatureSource[bool]
 	TokenExchange                   FeatureSource[bool]
-	Actions                         FeatureSource[bool]
 	ImprovedPerformance             FeatureSource[[]feature.ImprovedPerformanceType]
 	OIDCSingleV1SessionTermination  FeatureSource[bool]
 	DisableUserTokenEvent           FeatureSource[bool]