chore: Swingset-runner test to validate vat process failure behavior

Closes #2958

Author: FUDCo

packages/swingset-runner/demo/workerDeathTest/bootstrap.js

@@ -0,0 +1,14 @@
+import { E } from '@endo/eventual-send';
+import { Far } from '@endo/marshal';
+
+export function buildRootObject() {
+  console.log(`bootstrap vat initializing`);
+  return Far('root', {
+    async bootstrap(vats) {
+      const howMuch = 100_000_000;
+      console.log(`bootstrap vat invokes busy vat for ${howMuch} steps`);
+      await E(vats.busy).doStuff(howMuch);
+      await E(vats.idle).doNothing();
+    },
+  });
+}

packages/swingset-runner/demo/workerDeathTest/swingset.json

@@ -0,0 +1,15 @@
+{
+  "bootstrap": "bootstrap",
+  "defaultManagerType": "xs-worker",
+  "vats": {
+    "bootstrap": {
+      "sourceSpec": "bootstrap.js"
+    },
+    "busy": {
+      "sourceSpec": "vat-busy.js"
+    },
+    "idle": {
+      "sourceSpec": "vat-idle.js"
+    }
+  }
+}

packages/swingset-runner/demo/workerDeathTest/vat-busy.js

@@ -0,0 +1,22 @@
+import { Far } from '@endo/marshal';
+
+export function buildRootObject(_vatPowers, _vatParameters, baggage) {
+  console.log(`busy vat initializing`);
+  baggage.init('someKey', 'hello');
+  return Far('root', {
+    doStuff(howMuch) {
+      let n = 2.0;
+      for (let i = 0; i <= howMuch; i += 1) {
+        n = Math.sqrt(n) * Math.sqrt(n); // introduce some computational drag
+        if (i % 10_000_000 === 0) {
+          let bv = 'no baggage';
+          if (baggage) {
+            bv = baggage.get('someKey');
+          }
+          console.log(`busy vat doing step ${i} of ${howMuch}, bv=${bv}`);
+        }
+      }
+      console.log(`busy vat finished ${howMuch} steps`);
+    },
+  });
+}

packages/swingset-runner/demo/workerDeathTest/vat-idle.js

@@ -0,0 +1,8 @@
+import { Far } from '@endo/marshal';
+
+export function buildRootObject() {
+  console.log(`idle vat initializing`);
+  return Far('root', {
+    doNothing() {},
+  });
+}

packages/swingset-runner/src/main.js

@@ -339,10 +339,12 @@ export async function main() {
     delete config.loopboxSenders;
     deviceEndowments.loopbox = { ...loopboxEndowments };
   }
-  if (useXS) {
-    config.defaultManagerType = 'xs-worker';
-  } else {
-    config.defaultManagerType = 'local';
+  if (!config.defaultManagerType) {
+    if (useXS) {
+      config.defaultManagerType = 'xs-worker';
+    } else {
+      config.defaultManagerType = 'local';
+    }
   }
   if (launchIndirectly) {
     config = generateIndirectConfig(config);