macros, vm, bytecode: add #[primop] await-style primop macro

fix-vm/src/primops/stubs.rs

@@ -0,0 +1,9 @@
+//! Fallback definitions for the `#[primop]` surface syntax.
+//!
+//! `force`, `call`, and `spill` are recognized and rewritten by the
+//! `#[primop]` proc macro, so compiled code never calls them. They exist only
+//! so the un-expanded source name-resolves in tooling that does not run the
+//! macro (e.g. rust-analyzer while the macro crate is being rebuilt). Calling
+//! one for real is impossible: they never return.
+
+pub use crate::__macro_support::{call, force, spill};