Collect granular metrics for crate downloads and unpacks

[weihanglo]

Problem

-Zbuild-analysis has slowly become a replacement of the --timings feature. However, the current logger infra doesn't really take care of things outside actual compilation, and there is no way for users to inspect time spent in crate downloads and crates.

While downloads an decompressions are usually not a bottleneck for a cargo build run, they might still cause some issues in a slow network connection environment or an low IOPS hard disk / file system. It would be helpful if Cargo can provides these metrics.

Proposed Solution

Add new log message types in https://github.com/rust-lang/cargo/blob/b53c96b634c1ad10174a414c42287a4a399eec77/src/cargo/util/log_message.rs, and start collecting those metrics.

Notes

No response