Remove #[rust_stack]

[brson]

This is a hack that runs Rust code past the end of the stack. Nobody should ever be using it. We've had some discussions about strategies to remove it.

[z0w0]

Are the strategies for removing it documented somewhere?

[thestinger]

I think #[fast_ffi] is close to making this redundant. It can't mark a precise stack size a function requires though, and that may not easily be possible without LLVM patches.

cc @pcwalton

[huonw]

Triage visit: git log --grep 'rust_stack' and 'fast_ffi' don't indicate that any work has happened on this recently (although, segmented stacks are disabled with the new runtime), so there's nothing more I can add.

[thestinger]

This has been removed since segmented stack support has been dropped.