Update cargo dependency resolver to v2

[daxpedda]

This makes the wasm-bindgen project use resolver = "2", which already detected an issue in the CI, see #3358 (comment).

See the Cargo documentation for more info on this topic.

Fixes #3356.

[daxpedda]

I was surprised to see that wasm-bindgen actually still has std guards lying around, considering that no_std support was dropped a long time ago, see #2689.

I just removed the CI test for it, it wasn't actually testing it anyway, now that we use the new resolver it actually fails.
In a fit of insanity I had a brief attempt to actually fix the no_std built but turns out that it's not possible because some things actually rely on thread_local which isn't available in core or alloc.

[Liamolucko]

This seems reasonable, but it doesn't actually fix #3356. wit-validator is also a non-dev dependency of wasm-bindgen-cli-support, so this doesn't remove it from the dependency tree, plus rouille and walrus also have dependencies with future incompat warnings.

[daxpedda]

Hm, I think I was quite tired that night. Too bad, in any case upgrading the resolver is still a plus I guess.

[alexcrichton]

Thanks and sorry for the delay!