fix: memory leak (#7429)

Fix memory leak.

Two watchable.Maps were never closed when shutting down the provider:
- GatewayClassStatuses.Close() - missing in GatewayAPIStatuses.Close()
- BackendTrafficPolicyStatuses.Close() - missing in PolicyStatuses.Close()

Each unclosed map leaked 3 goroutines:
1. Internal watchable.Map.coalesce goroutine
2. HandleSubscription goroutine blocked on channel read
3. Error handler goroutine blocked on channel read

Signed-off-by: Gonzalo Serrano <boikot@gmail.com>
Signed-off-by: zirain <zirain2009@gmail.com>

Author: gonzaloserrano

internal/message/types.go

@@ -85,6 +85,7 @@ type GatewayAPIStatuses struct {
 }
 
 func (s *GatewayAPIStatuses) Close() {
+	s.GatewayClassStatuses.Close()
 	s.GatewayStatuses.Close()
 	s.HTTPRouteStatuses.Close()
 	s.GRPCRouteStatuses.Close()
@@ -116,6 +117,7 @@ type ExtensionStatuses struct {
 
 func (p *PolicyStatuses) Close() {
 	p.ClientTrafficPolicyStatuses.Close()
+	p.BackendTrafficPolicyStatuses.Close()
 	p.SecurityPolicyStatuses.Close()
 	p.EnvoyPatchPolicyStatuses.Close()
 	p.BackendTLSPolicyStatuses.Close()