Add details to InstanceError and CreateSurfaceError.

[kpreid]

Checklist

• Update all backends
• Add tests where feasible, such as WebGL and WebGPU canvas errors
• Run cargo clippy.
• Run cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md.

Connections
Followup to #3052.

Description
This will allow developers, particularly those in communication with users with hardware they don't own, to diagnose “why won't this work on my machine” better, without needing to obtain logs in addition to the error value.

Note that this is a semver-breaking change because InstanceError and CreateSurfaceError no longer implement PartialEq. This could be avoided by pointer comparison of the internal Arc, but I think it is more typical Rust to not implement PartialEq for error types unless there is a strong motivation to and their contents are tightly controlled.

Testing
Ran cargo nextest run; CI will check other platforms.

[kpreid]

This PR is in principle ready to merge, but I am hoping to get around to writing tests for the canvas.getContext() errors before I mark it ready.

[kpreid]

I've added a test for create_surface_from_canvas() under WebGL and WebGPU. However, a certain amount of persuasion was required for tests/src/lib.rs to cooperate with the custom canvas creation. Please review carefully (and CI will hopefully tell us if the cfgs are wrong).

[kpreid]

That clippy::redundant_clone lint that failed in CI is completely bogus — the code wouldn't compile (and would be wrong) without it, since SurfaceGuard has a Drop. I've allowed it.

[kpreid]

Ping? This should be ready to go now.

Also, I have belatedly realized that I want to do exactly the same thing to RequestDeviceError — would you prefer that be folded into this PR or separate?

[cwfitzgerald]

This is beautiful stuff!