[feature request]improve configuration of concurrent pod-binding workers

[rambohe]

What would you like to be added:

please refer to pull request #1906 and improve podbinding-controller configuration for podbinding controller in yurt-manager component.

openyurt/pkg/yurtmanager/controller/yurtcoordinator/podbinding/podbinding_controller.go

Line 41 in ed20955

 flag.IntVar(&concurrentReconciles, "podbinding-controller", concurrentReconciles, "Max concurrent workers for podbinding-controller controller.") 

others
/kind feature

[Leo Huang]

/assign @huangchenzhao