feat: mirrorz.json d extension

[ZenithalHourlyRate]

A mirror site can have many domain names for different purposes. e.g. https://cernet.mirrors.ustc.edu.cn and https://mirrors4.tuna.tsinghua.edu.cn

This ability has been covered by mirrorz-d-extension

We should enable users to specify a more detailed domain name instead of the generic site.url, with each endpoint showing its ability

Expected UI (to be discussed):

Select mirror: TUNA
Select domain: tuna4 (IPv4, SSL, NOSSL)

If it is not public

Select mirror: UESTC
Select domain: uestc (NOT PUBLIC) (IPv4, SSL, NOSSL)