Support configuring cluster domain in the TidbCluster CR

[DanielZhangQD]

Feature Request

Is your feature request related to a problem? Please describe:

• Some users may customize the cluster domain of the Kubernetes cluster, e.g. test.local instead of cluster.local
• For across kubernetes deployment, we have to set full addresses for each pod and service, e.g. ns0-pd-0.ns0-pd-peer.ns0.svc.test.local

Describe the feature you'd like:

Support configuring cluster domain in the TidbCluster CR, and set full addresses for each pod and service when the cluster domain is configured.
Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[DanielZhangQD]

Please note that if the cluster domain is not configured in the CR, there should be no changes to the current behavior and the cluster should not be rolling updated after upgrading TiDB Operator to the version including this feature.

[mikechengwei]

I can complete this feature because I have this requirement. I have mentioned similar issues #1366 which is closed

[L3T]

/assign