cargo.build, the WASI test runner, the console, and core.notify ordering

- cargo.build (native): one source copy, tests under WASI, release
  build to /state/cargo/builds/<n>/, process groups killed on cancel.
  The host writes the SDK copy to /plugins/cargo/sdk/ at start.
- sausage test-runner: one instance per test, in parallel, with its own
  mount table (empty world, package folder at its path); answers
  core.lock, core.unlock, core.notify, core.log.
- The console: rustyline, notifications while typing, ls/cat through the
  process view, methods, ps, log, activate, revert, stop, kill.
- core.notify on stdout is handled in order, before the response.

cli/tests/crates/cargo-test-fail/src/main.rs

@@ -1,9 +1,13 @@
+//! A panic must not prevent the runner from executing another test.
 fn main() {}
-
 #[cfg(test)]
 mod tests {
     #[test]
-    fn deliberate_unit_test_failure() {
-        assert_eq!(2 + 2, 5);
+    fn a_panics() {
+        panic!("deliberate WASI panic");
+    }
+    #[test]
+    fn z_survives() {
+        assert_eq!(2 + 2, 4);
     }
 }