Create a WASI dev container configuration

[brettcannon]

Now that we have a separate WASI dev container, we can have a separate configuration here. It won't interfere with the default configuration and doesn't get in the way of people using Codespaces as it requires more effort to select the WASI configuration.

If a configuration gets merged I will turn on pre-builds for this configuration as well like we have for the default one (I already checked with Ee at the core dev sprints and our current pre-builds are so cheap that they don't even register as an expense, so one more was given a go-ahead).

Linked PRs

• GH-140472: Create a WASI devcontainer configuration #140473