[wgpu-hal] Change the DropCallback API to use FnOnce instead of FnMut

[jerzywilczek]

Connections
This refines the change I made in #6164

Description
I initially made the DropCallback API use FnMut. This seemed like a good choice at the time, since we only get &mut self access to the DropGuard in its Drop implementation. After some time it became apparent to me that at least a part of the users of this API will want to supply a closure which just holds some kind of a reference-counted wrapper around the corresponding resource that would drop it when called, thus freeing the resource. With the current API they have to do weird stuff to achieve this behavior, because FnMut cannot consume its captures:

let mut vulkan_device_clone: Option<Arc<VulkanDevice>> = Some(vulkan_device.clone());
let wgpu_device = unsafe {
    wgpu_adapter.adapter.device_from_raw(
        ...
        Some(Box::new(move || { vulkan_device_clone.take(); })),
        ...
    )?
};

With this change they could consume the capture:

let vulkan_device_clone: Arc<VulkanDevice> = vulkan_device.clone();
let wgpu_device = unsafe {
    wgpu_adapter.adapter.device_from_raw(
        ...
        Some(Box::new(move || { vulkan_device_clone; })),
        ...
    )?
};
// or more explicitly:
let wgpu_device = unsafe {
    wgpu_adapter.adapter.device_from_raw(
        ...
        Some(Box::new(move || { drop(vulkan_device_clone); })),
        ...
    )?
};

This seems a lot more intuitive.

Testing
Things still compile and there is no difference in test passes.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
    This just fails
• Run cargo xtask test to run tests.
  129 tests fail on my machine, with or without the changes
• Add change to CHANGELOG.md. See simple instructions inside file.

[cwfitzgerald]

Nice!