Remove parking_lot dependency

[nicoburns]

std::sync::Mutex now has comparable performance

[mrobinson]

Is this the case on all platforms. I understood that the performance was comparable only on some.

[nicoburns]

Hmm... I was unable to define any definitive information on this:

• https://blog.rust-lang.org/2022/06/30/Rust-1.62.0.html#thinner-faster-mutexes-on-linux suggests that std Mutex is now fast on Linux.
• The linked tracking issue does not obviously say anything about the current state of windows or macOS Tracking issue for improving std::sync::{Mutex, RwLock, Condvar} rust-lang/rust#93740
• Winit has switched back to std (but there are no numbers) Remove parking_lot dependency rust-windowing/winit#2423
• Tokio has parking_lot behind an off-by-default feature.