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/command/instance_features.go

@@ -21,7 +21,6 @@ type InstanceFeatures struct {
 	LegacyIntrospection             *bool
 	UserSchema                      *bool
 	TokenExchange                   *bool
-	Actions                         *bool
 	ImprovedPerformance             []feature.ImprovedPerformanceType
 	WebKey                          *bool
 	DebugOIDCParentError            *bool
@@ -39,7 +38,6 @@ func (m *InstanceFeatures) isEmpty() bool {
 		m.LegacyIntrospection == nil &&
 		m.UserSchema == nil &&
 		m.TokenExchange == nil &&
-		m.Actions == nil &&
 		// nil check to allow unset improvements
 		m.ImprovedPerformance == nil &&
 		m.WebKey == nil &&