Investigate storage backend with CloudFlare's R2

[brainstorm]

Summary of the investigation(s): https://twitter.com/braincode/status/1616272750792048647

Conclusions:

Option 1: If we don't mind having AWS+R2 setup, this could work since R2 supports S3 API fairly well, avoiding the need to write a R2-specific htsget storage backend.

Option 2: If we want a R2-Workers combo (S3 + lambda equivalent), we'd need to write a htsget-cloudflare crate and make sure we don't activate tokio functionality in any of the dependencies (i.e noodles).

Option 1 is shippable fast, Option 2 is more maintainable.