[feature request] Store node name in v1beta2.Nodepool spec

[tnsimon]

What would you like to be added:
Store node name in v1beta2.Nodepool spec.

Why is this needed:
When yurt-hub starts, it needs to know whether it is the leader. Currently only the node Internal Ip is stored. Keeping the node name also will help.

others
/kind feature

[tnsimon]

/assign @tnsimon

[rambohe-ch]

@tnsimon Yes, It's a good idea to add node name information into leader endpoints, then Yurthub component can resolve this information for deciding the forwarded destination of requests for pool scope requests(like list/watch services, endpointslices).