Drop dependency of TiDB for host info

[breezewish]

Feature Request

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

Currently host info send queries to TiDB, which has several disadvantages:

1. The instance list may not be identical with the one in "instance" tab
2. Doesn't work when there is no TiDB
3. More potential bugs: A TiDB bug will break the functionality as well, even if original API works well.

Describe the feature you'd like:

Update the host info module to call debug API of each component directly.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[baurine]

I didn't find the implemented debug API to get host info in pd/tidb/tikv repos (only found /debug/pprof), so we should implement the API in pd/tidv/tikv first?

[breezewish]

The implementation for TiDB and PD is in https://github.com/pingcap/sysutil.

We can start from dropping the dependency of CLUSTER_INFO table first, then CLUSTER_HARDWARE.