Removed once_cell usage where possible now that Mutex::new and RwLock…

[vahanbgs]

…:new are const fns

• Tested on all platforms changed
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[vahanbgs]

Requires Rust 1.63 to compile, that's why CI checks are failing

[madsmtm]

Yeah, see #2453 for a bit of discussion.

In short, I expect that we'll first be able to include in around ~6 months when distros have caught up, so some time around February. Thanks though!

[kchibisov]

There's no intention of using 1.63 in a near future.