Remove the util crate
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This PR removes the `util` crate.
* Replaced the `spawn_named` and `clamp` functions by appropriate uses of `std:🧵:Builder::spawn`, `std::cmp::min` and `std::cmp::max`.
* Moved `opts`, `prefs` and `resource_files` into a new `config` crate.
* Moved `remutex` and `geometry` into their own crates.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because they are refactorings
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