tiup cluster check: support port connectivity check

[pcqz]

Feature Request

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

The ports required by tidb cluster is prohibited default by firewall in the case of cross-region deployment. After tiup cluster deployment, tiup cluster display result is normal when all nodes status are up, but connection between cluster nodes may fail.

Describe the feature you'd like:
I'd like that tiup cluster check can not only check port occupancy, but also perform port connectivity check.

Why the featue is needed:
In order to achieve cross-cloud high availability, users may deploy cluster in the public network environment.

Describe alternatives you've considered:
Login to each node and use Telnet command to check port connectivity.

Teachability, Documentation, Adoption, Migration Strategy:

[dveeden]

Related: #1087