Cluster Diagnosis GA Test

[lilyjazz]

Feature Request

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

Cluster Diagnosis and SQL Diagnosis are still not GA yet. The two features should be GA for users.

user doc: https://docs.pingcap.com/zh/tidb/stable/information-schema-sql-diagnostics and https://docs.pingcap.com/zh/tidb/stable/dashboard-diagnostics-access

The FRC of feature: https://github.com/pingcap/tidb/blob/master/docs/design/2019-11-14-tidb-builtin-diagnostics-zh_CN.md

Describe the feature you'd like:

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[lilyjazz]

assignee to @Hawkson-jee