improve infrastrucutre around downloads stats retrieval

[crowlKats]

• improve caching, include the downloads metrics to be cached 1h
• implement rateliming
• implement a way to retrieve data in bulk (ie bulk downloads, package names, and such)

[AugustinMauroy]

question as contributor, which part of the codebase handle that.

[crowlKats]

this involves various parts of the rust codebase, and also some bigquery work