Update archive-coverage and autopkgtest for loong64

• About archive-coverage

The number of Installed packages for loong64 is 16544. And loong64's archive-coverage is over 95%, the specific data is 95.29%.

Please see https://buildd.debian.org/stats/graph-ports-quarter-big.png.

• About Debian debci

We have prepared 2 debci machines (LoongArch Server machines) for debci team.

Please see https://lists.debian.org/debian-ci/2024/05/msg00012.html.

Currently loong64 was included in Debian Continuous Integration. Thanks elbrus, sincerely.

The build status of debci can be found at https://ci.debian.net/user/britney/jobs?package=&trigger=&suite%5B%5D=unstable&arch%5B%5D=loong64&page=202.

Please review. Thanks, Dandan Zhang