Support different ways of retrieving crates latest versions instead via relying on crates.io APIs (to limit load on their servers and prevent abuse)

[vi]

According to the source code it gets latest versions of crates not from the index (like cargo update or the cargo outdated tool), but directly from crates.io.

I think in addition to failing to automatically support custom registries, it may spam crates.io with potentially repeated numerous requests (for example, if end user starts cargo interactive-update multiple times to update dependencies step by step).

Maybe newest versions retrieval should rely on Cargo, not directly on Crates.io, e.g. using a temporary project like in cargo-outdated?

[BenJeau]

I don't think it would be considered abused as part of the tool itself, but more on the user using the tool. We could add some caching/disclaimer about this though.

I'm not opposed to finding different ways to accomplish the update process if there's other ways.