mirrors.yml: various updates - remove `tencent` mirror, sync discontinued by downstream - remove `koddos-hk`, sync discontinued by downstream - add `repo-us`, AOSC's repository mirror in US - add `bfsu4` and `bfsu6`, BFSU's v4/v6 only domain - add `pku`, Peking University's Mirror - add `qlut`, Qilu University of Technology's Mirror - add `cernet`, CERNET mirrors' redirection service with IP-based optimization - use https for `tsukuba` and `jlu` mirror - declare `xtom` mirror's location in US - add /anthon/ suffix for `origin`, `origin4`, `origin6` and `fastly` - fix some typo