Update toolchain to nightly 2024-11-15

[dbittman]

This PR updates the toolchain to a recent nightly version and replaces the old twizzler-runtime-api crate with a new design based on bindgen that should improve interoperability with other languages, improve stability, etc. The update also gains a lot of nice functionality from new Rust features. We also have a more robust support for basic C code, allowing libunwind to be more than a black-box.

See also: #217

A couple things to note:

• Most of the churn here comes from unstable features changing in subtle ways and having to keep up, as well as the new ABI crate changing paths to types and stuff.
• This PR also includes an update to xtask that will make it check for ABI version compatibility between the installed toolchain and the source tree. What this means is that once someone pulls this update, they may need to run cargo bootstrap, but xtask should detect this and stop the build with a helpful error message.
• To try to keep the churn down, this PR does not update the reference runtime as needed for the new ABI work. This means that it has been disabled in the build. This is fine, since tests were not dependent on that yet. Fortunately, the updates needed to the reference runtime coincide with updates needed for the security monitor work, which I'm making the PRs for this week.

[gvnn3]

Much as this is HUGE it is also mostly mechanical so let's get this in and move on.

[gvnn3]

Why comment instead of remove?

[dbittman]

Because they'll come back in the next PR