Updating GATTServer's Connect/Disconnect calls
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Added the missing [Step 5.2.3](https://github.com/servo/servo/compare/master...szeged:connect-disconnect-update#diff-1dbe29f87740f5aec93f37adbecace6cR213) to the `connect` function.
Updated the [disconnect](https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetoothremotegattserver-disconnect) function to its current state in the specification, including the `clean_up_disconnected_device` and the `garbage_collect_the connection` functions.
Added new tests for checking the invalid state of JS objects after disconnection.
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They're not at all related, besides both being asynchronous. This change adds
a little extra code in response_async(), but makes this code more readable
and reduces the unnecessary indirection.
This change also makes the build system slightly more parallel, by dropping
the dependency on bluetooth_traits from net_traits.
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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<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [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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