Optimize the 'Cluster Status' page

[patrickluoyu]

The Cluster Status page has the following problems:

• Titles such as etcd Client Traffic are split into three elements of different sizes, which could make translation impossible.
• In the Service Status area, External etcd makes no sense; Leader exists and Leader changes in 1h are repeated; Leader exists is unnecessary because there is a Leader tag for the etcd leader.

Please optimize the Cluster Status page if possible.

/assign @VioZhang @zryfish @harrisonliu5