Support priority field in Route module

[juzhiyuan]

Feature request

Please describe your feature

Users could use the priority field to do some actions like a grayscale release.

Describe the solution you'd like

1. Add that field in the Route module.

Describe alternatives you've considered

None

Additional context

None

[juzhiyuan]

cc @nic-chen I remember the manager-api supports this field, right?

cc @membphis

[membphis]

need @nic-chen 's confirm. manager-api should support this field, same as admin api

[nic-chen]

cc @nic-chen I remember the manager-api supports this field, right?

cc @membphis

sure, it has supported.