Make the rate_limiter Crate Fully Independent

[alexandruag]

The rate_limiter crate still has an internal dependency on our logger crate, which is not going to be published on crates.io as a separate library. We should remove this and any kind of logging altogether (addressing #259 in the process would definitely help) before rate_limiter can be considered independent.

[acatangiu]

Our logger crate might need to go on crates.io as well. Of course after separating Firecracker specific code inside it and making that plugable. But this is a decision we need to make after looking at the whole codebase and our uses of logger.

[georgepisaltu]

This is discussed in rust-vmm/community#107 . Closing this