windows: add Service.ListDependentServices

This method allows a user to list all Windows services which are
dependent upon a given service.

This commit makes use of the EnumDependentServices Windows API call.
Without this, a user would have to iterate through each service on the
system, and check if the given service is listed in each service's
dependencies list.

The implementation of ListDependentServices is mostly the same as
Mgr.ListServices, as the API calls behave in the same way.

Fixes golang/go#56766

Change-Id: I9ec18c97afd02f48deef691ccdd5c26d6501add1
Reviewed-on: https://go-review.googlesource.com/c/sys/+/451363
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

windows/service.go

@@ -141,6 +141,12 @@ const (
 	SERVICE_DYNAMIC_INFORMATION_LEVEL_START_REASON = 1
 )
 
+type ENUM_SERVICE_STATUS struct {
+	ServiceName   *uint16
+	DisplayName   *uint16
+	ServiceStatus SERVICE_STATUS
+}
+
 type SERVICE_STATUS struct {
 	ServiceType             uint32
 	CurrentState            uint32
@@ -245,3 +251,4 @@ type QUERY_SERVICE_LOCK_STATUS struct {
 //sys	UnsubscribeServiceChangeNotifications(subscription uintptr) = sechost.UnsubscribeServiceChangeNotifications?
 //sys	RegisterServiceCtrlHandlerEx(serviceName *uint16, handlerProc uintptr, context uintptr) (handle Handle, err error) = advapi32.RegisterServiceCtrlHandlerExW
 //sys	QueryServiceDynamicInformation(service Handle, infoLevel uint32, dynamicInfo unsafe.Pointer) (err error) = advapi32.QueryServiceDynamicInformation?
+//sys	EnumDependentServices(service Handle, activityState uint32, services *ENUM_SERVICE_STATUS, buffSize uint32, bytesNeeded *uint32, servicesReturned *uint32) (err error) = advapi32.EnumDependentServicesW