Fixed#1310
Also add rename `fetch_crate_cratesio` => `fetch_crate_cratesio_api` and
put it behind a new feature `crates_io_api`.
Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
Fixed#1295
The 1 request per second rate-limit is too strict and it makes
`cargo-binstall` very slow when resolving many crates in parallel.
Relying on the rate-limit in `binstalk_downloader::remote::Client`
should be good enough.
Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>