Add WASM tests to CI

[shssoichiro]

As noted in #3359, we want to add tests in CI to verify wasm, both on stable and minimum supported rustc versions.

[FreezyLemon]

We spent some time on improving the CI jobs in rust-av recently, so I can take a look at this. It should be good enough to run cargo check for MSRV purposes, right? I don't think we'd expect changes that don't break the build and change runtime behaviour

[lu-zero]

it should be fine, -Zmsrv-policy in nightly might be an alternative otherwise.