Refactor for wgpu v23 compatibility with an example of wgpu device sharing

[AsherJingkongChen]

Related Issues/PRs

• Refactor for wgpu v23 compatibility burn#2435
• Remove IDs from wgpu traits gfx-rs/wgpu#6134
• v23.0.0 release gfx-rs/wgpu#6465

Checklist

• Confirmed that cargo xtask test --ci script has been executed.
• Made sure the book is up to date with changes in this PR.
• Checked for any updates or changes in dependencies.

Changes

1. Modified entry_point Type

• Change: Updated the type of entry_point from &str to Option<&str>.
• Reason: Clippy's suggestion

2. Updated WgpuDevice::Existing Enum Type

• Change: Altered the type of WgpuDevice::Existing from wgpu::Id<wgpu::Device> to u32.
• Reason: After the changes introduced in gfx-rs/wgpu#6134, wgpu::Id no longer exists. Using a u32 ensures a unique identifier for WgpuDevice::Existing.

Note: We avoid using pointers as identifiers due to the possibility of reallocation at the same memory address. To maintain uniqueness, a monotonically increasing value is now used internally.

Examples

1. Added device_sharing Example
   • Description: This example demonstrates the device sharing feature.
   • How to Run: Use the following command to run the example:

     cargo run --example device_sharing --features wgpu

[ArthurBrussee]

This seems a bit dangerous! No guarantee your next device doesn''t land on the same memory adress - not unlikely even depending how you allocate stuff.

I think maybe just keeping an AtomicU64 which is incremented might be easier. Do have to be careful not to register something twice but that's already the case I think.

(sorry for the driveby comment - I added this code originally)

[AsherJingkongChen]

The code should explain your concerns, it does reallocation on the same address:

No guarantee your next device doesn't land on the same memory address.

fn main() {
    let mut x = String::from("Hello, world!");
    let addr_x1 = &x as *const _ as usize;
    drop(x);
    x = String::from("Bonjour, le monde!");
    let addr_x2 = &x as *const _ as usize;
    assert_eq!(addr_x1, addr_x2);
}

[ArthurBrussee]

Well, exactly - two different strings and yet the adress is the same. So, in this case - you could feasible create two different wgpu devices and yet have Cube think the are the same WgpuDevice, that's not good! The id should be unique.

[AsherJingkongChen]

Now I use monotonically increasing value in init_existing_device just like other id generators in CubeCL. Besides, I noticed that I didn't update SPIR-V compiler's init_existing_device.