maint: Avoid loading shared libraries more than once

[notgull]

• [x] Tested on an x11 machine
• [x] Compilation warnings were addressed
• [x] cargo fmt has been run on this branch
• [x] cargo doc builds successfully
• [x] Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• [x] Updated documentation to reflect any user-facing changes
• [x] Created or updated an example program if it would help users understand this functionality

This PR makes it so the X11 linked libraries are only loaded once. This PR also replaces lazy_static with the once_cell crate, since lazy_static has largely been replaced with once_cell within the Rust ecosystem.

[notgull]

@AltF02 Any chance you could take another look at this? This is a soundness issue as much as a convenience issue, since it gets rid of the bespoke unsafe code for shared library initialization.

[AltF02]

Hi, excuses. I was very busy the past weeks

[AltF02]

Released under v2.21.0