Refactor `requestTokenToZts()`

[WindzCUHK]

k8s-athenz-sia/pkg/token/daemon.go

Line 165 in f6de56a

func (d *daemon) requestTokenToZts(k CacheKey, m mode, requestID string) (GroupDoResult, error) {

1. split access token and role token group object to shorten the key
2. merge UniqueId() and String() function