TidbInitializer support specifying tidb endpoint

[tennix]

Feature Request

For a cluster enabling SEM (Security Enhanced Mode), the tidb-server have limited permission, if we want to do some initialization that beyond SEM tidb-servers permissions, we have two choices:

• Disable SEM first and then run initialization SQL statement and then restart tidb to enable SEM
• Run TidbInitializer via a SEM disabled tidb-server, after that shut down SEM disabled tidb-server

The first one need to rolling restart all tidb-servers which might take a long time. While with the second one, TidbInitializer currently only support finding tidb-server endpoint via TidbCluster, so it's impossible to do the initialization via TidbInitializer.

So I'd like to allow user specifying a tidb endpoint for TidbInitializer.

[mikechengwei]

apiVersion: pingcap.com/v1alpha1
kind: TidbInitializer
metadata:
  name: initialize-demo
spec:
  image: tnir/mysqlclient
  imagePullPolicy: IfNotPresent
  cluster:
    name: initialize-demo
    host:
    port:

Do you me above example code?