Henry LONNG

This PR is so big, could you please split it into some smalls?

@asddongmen Can we merge the two packages?

@BusyJay How about adding a `tiup alias` subcommand to create a shortcut for specific component. 1. `tiup alias ticluster cluster` -> shortcut to the latest version of the cluster component...

Still working in progress?

@cyliu0 Thanks for this suggestion. It's a good idea to distinguish the environment variable and `tiup mirror set` subcommand. I think we can change the behavior according to your suggestion.

@lucklove It's better to keep it in 1.x and remove it at 2.x.

目前还是 Draft 阶段，希望大家积极提出建议，然后会成为社区的第一个开源项目大家一起参与。

@hermitsgame Are you interested to contribute it?

@cosven Please replace the image in the describtion which contains Chinese.

Can you use the WSL environment?