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/feature/feature.go

@@ -15,7 +15,7 @@ const (
 	KeyLegacyIntrospection
 	KeyUserSchema
 	KeyTokenExchange
-	KeyActions
+	KeyActionsDeprecated
 	KeyImprovedPerformance
 	KeyWebKey
 	KeyDebugOIDCParentError
@@ -46,7 +46,6 @@ type Features struct {
 	LegacyIntrospection             bool                      `json:"legacy_introspection,omitempty"`
 	UserSchema                      bool                      `json:"user_schema,omitempty"`
 	TokenExchange                   bool                      `json:"token_exchange,omitempty"`
-	Actions                         bool                      `json:"actions,omitempty"`
 	ImprovedPerformance             []ImprovedPerformanceType `json:"improved_performance,omitempty"`
 	WebKey                          bool                      `json:"web_key,omitempty"`
 	DebugOIDCParentError            bool                      `json:"debug_oidc_parent_error,omitempty"`