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/integration/client.go

@@ -763,7 +763,7 @@ func (i *Instance) DeleteExecution(ctx context.Context, t *testing.T, cond *acti
 	require.NoError(t, err)
 }
 
-func (i *Instance) SetExecution(ctx context.Context, t *testing.T, cond *action.Condition, targets []*action.ExecutionTargetType) *action.SetExecutionResponse {
+func (i *Instance) SetExecution(ctx context.Context, t *testing.T, cond *action.Condition, targets []string) *action.SetExecutionResponse {
 	target, err := i.Client.ActionV2beta.SetExecution(ctx, &action.SetExecutionRequest{
 		Condition: cond,
 		Targets:   targets,