Support customized extra side header

[breezewish]

Feature Request

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

In TiDB Cloud it is hard to know which TiDB Dashboard we are looking at.

Describe the feature you'd like:

It would be great if some extra information can be displayed in the sidebar. For example, displaying the tidb cloud organization and cluster name.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy: