tests: fast host suites

The timing rules are in two tests (upgrade_and_discovery_deadlines,
stop_deadlines). All other tests use a grace period of 0 or core.stop,
poll with deadlines instead of sleeping, and use the persistent cache in
CARGO_TARGET_TMPDIR. The 128-cycle singleton test is an ignored stress
test that nix flake check runs; the normal run has a 4-cycle sample.
Warm, the activation suite takes 12 s (was 47 s), and cargo test
--workspace takes 65 s.

cli/tests/plugins/activation/src/main.rs

@@ -11,8 +11,9 @@ fn deferred(request: &Value, plugin: &str, lines: &mut impl Iterator<Item = io::
     send(
         json!({"jsonrpc":"2.0","id":request["id"],"result":std::env::var("SAUSAGE_PID").unwrap()}),
     );
+    let before = std::time::Instant::now();
     while !std::path::Path::new(&format!("/state/{plugin}/release-call")).exists() {
-        std::thread::sleep(std::time::Duration::from_millis(1));
+        assert!(before.elapsed() < std::time::Duration::from_secs(30));
     }
     send(json!({"jsonrpc":"2.0","id":"deferred","method":"notes.legacy","params":{}}));
     for line in lines {
@@ -57,10 +58,15 @@ fn main() {
             return;
         }
         "rpc.discover" => {
+            if document["x-test-no-answer"] == true {
+                for _ in &mut lines {}
+                return;
+            }
             if document["x-test-wait"] == true {
                 std::fs::write(format!("/state/{plugin}/discover-started"), "ready").unwrap();
+                let before = std::time::Instant::now();
                 while !std::path::Path::new(&format!("/state/{plugin}/discover-release")).exists() {
-                    std::thread::sleep(std::time::Duration::from_millis(1));
+                    assert!(before.elapsed() < std::time::Duration::from_secs(30));
                 }
             }
             document
@@ -105,8 +111,9 @@ fn main() {
     send(json!({"jsonrpc":"2.0","id":request["id"],"result":result}));
     if request["method"] == "rpc.discover" && result["x-test-linger"] == true {
         if result["x-test-stubborn"] == true {
+            let before = std::time::Instant::now();
             while !std::path::Path::new(&format!("/state/{plugin}/discovery-exit")).exists() {
-                std::thread::sleep(std::time::Duration::from_millis(1));
+                assert!(before.elapsed() < std::time::Duration::from_secs(30));
             }
         } else {
             for _ in lines {}