clustermesh: reset remote clusters configuration upon disconnection

cilium/cilium#28763 decoupled the helm settings to enable the
clustermesh-apiserver and provide the list of clusters to connect to.
Let's reflect this change to the 'cilium clustermesh disable' command
as well, explicitly disabling and resetting the remote clusters configs
when invoked, to correctly disconnect from possible leftover clusters.

Fixes: cilium/cilium#32300
Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>

clustermesh/clustermesh.go

@@ -1521,6 +1521,8 @@ func EnableWithHelm(ctx context.Context, k8sClient *k8s.Client, params Parameter
 func DisableWithHelm(ctx context.Context, k8sClient *k8s.Client, params Parameters) error {
 	helmStrValues := []string{
 		"clustermesh.useAPIServer=false",
+		"clustermesh.config.enabled=false",
+		"clustermesh.config.clusters=null",
 		"externalWorkloads.enabled=false",
 	}
 	vals, err := helm.ParseVals(helmStrValues)