Move Throwable catch to ExtraProtobufGenerator.run (#1637)

This catches errors that happen at any point in
`ExtraProtobufGenerator.run`, not just within
`handleCodeGeneratorRequest`. This, in turn, prevents more cases of
`ProtoScalaPBRule` aspect workers hanging. Part of #1482.

As I started experimenting with updating gRPC and ScalaPB libs, I bumped
the ScalaPB libs to 1.0.0-alpha.1 to try to resolve a problem. The
`ProtoScalaPBRule` workers then started hanging again.

After pulling the `catch ... Throwable` block from #1630 up into
`ExtraProtobufGenerator.run`, I got the following stack trace:

```txt
$ bazel build //test/proto/...

ERROR: .../external/com_google_protobuf/BUILD.bazel:334:14:
  ProtoScalaPBRule
  external/com_google_protobuf/wrappers_proto_jvm_extra_protobuf_generator_scalapb.srcjar
  failed: (Exit 1): scalapb_worker failed: error executing command
  (from target @com_google_protobuf//:wrappers_proto)

bazel-out/.../bin/src/scala/scripts/scalapb_worker
  ... (remaining 2 arguments skipped)

--jvm_extra_protobuf_generator_out: java.lang.IllegalAccessError:
  class scalapb.options.Scalapb$ScalaPbOptions tried to access method
  'com.google.protobuf.LazyStringArrayList
    com.google.protobuf.LazyStringArrayList.emptyList()'
  (scalapb.options.Scalapb$ScalaPbOptions and
   com.google.protobuf.LazyStringArrayList are in unnamed module
   of loader 'app')
      at scalapb.options.Scalapb$ScalaPbOptions.<init>(Scalapb.java:5021)
      at scalapb.options.Scalapb$ScalaPbOptions.<clinit>(Scalapb.java:11165)
      at scalapb.options.Scalapb.<clinit>(Scalapb.java:24184)
      at scalapb.options.compiler.Scalapb$.registerAllExtensions(Scalapb.scala:8)
      at scalarules.test.extra_protobuf_generator.ExtraProtobufGenerator$.run(ExtraProtobufGenerator.scala:48)
      at protocbridge.frontend.PluginFrontend$.$anonfun$runWithBytes$1(PluginFrontend.scala:51)
      at scala.util.Try$.apply(Try.scala:213)
      at protocbridge.frontend.PluginFrontend$.runWithBytes(PluginFrontend.scala:51)
      at protocbridge.frontend.PluginFrontend$.runWithInputStream(PluginFrontend.scala:121)
      at protocbridge.frontend.PosixPluginFrontend$.$anonfun$prepare$2(PosixPluginFrontend.scala:40)
      at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
      at scala.concurrent.impl.ExecutionContextImpl$DefaultThreadFactory$$anon$1$$anon$2.block(ExecutionContextImpl.scala:75)
      at java.base/java.util.concurrent.ForkJoinPool.managedBlock(ForkJoinPool.java:3118)
      at scala.concurrent.impl.ExecutionContextImpl$DefaultThreadFactory$$anon$1.blockOn(ExecutionContextImpl.scala:87)
      at scala.concurrent.package$.blocking(package.scala:146)
      at protocbridge.frontend.PosixPluginFrontend$.$anonfun$prepare$1(PosixPluginFrontend.scala:38)
      at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
      at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:659)
      at scala.util.Success.$anonfun$map$1(Try.scala:255)
      at scala.util.Success.map(Try.scala:213)
      at scala.concurrent.Future.$anonfun$map$1(Future.scala:292)
      at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:42)
      at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:74)
      at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
      at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
      at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
      at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
      at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
      at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

java.lang.RuntimeException: Exit with code 1
     at scala.sys.package$.error(package.scala:30)
     at scripts.ScalaPBWorker$.work(ScalaPBWorker.scala:44)
     at io.bazel.rulesscala.worker.Worker.persistentWorkerMain(Worker.java:96)
     at io.bazel.rulesscala.worker.Worker.workerMain(Worker.java:49)
     at scripts.ScalaPBWorker$.main(ScalaPBWorker.scala:39)
     at scripts.ScalaPBWorker.main(ScalaPBWorker.scala)

ERROR: .../external/com_google_protobuf/BUILD.bazel:334:14
  scala @com_google_protobuf//:wrappers_proto failed:
  (Exit 1): scalapb_worker failed: error executing command
  (from target @com_google_protobuf//:wrappers_proto)

bazel-out/.../bin/src/scala/scripts/scalapb_worker
  ... (remaining 2 arguments skipped)
```

Bumping to protobuf v28.2 resolved the issue, at the expense of
sacrificing Bazel 6 support, as v21.7 was the last to support Bazel 6.
But this issue is orthogonal to the original gRPC test failure issue,
which I'll address in a future change.

test/src/main/scala/scalarules/test/extra_protobuf_generator/ExtraProtobufGenerator.scala

@@ -41,14 +41,30 @@ class CustomProtobufGenerator(
 
 object ExtraProtobufGenerator extends ProtocCodeGenerator {
    override def run(req: Array[Byte]): Array[Byte] = {
-    val registry = ExtensionRegistry.newInstance()
-    Scalapb.registerAllExtensions(registry)
-    val request = CodeGeneratorRequest.parseFrom(req)
-    handleCodeGeneratorRequest(request).toByteArray
+    val b = CodeGeneratorResponse.newBuilder
+
+    try {
+      val registry = ExtensionRegistry.newInstance()
+      Scalapb.registerAllExtensions(registry)
+      val request = CodeGeneratorRequest.parseFrom(req)
+      handleCodeGeneratorRequest(request, b)
+
+    } catch {
+      case e: Throwable =>
+        // Yes, we want to catch _all_ errors and send them back to the
+        // requestor. Otherwise uncaught errors will cause the generator to
+        // die and the worker invoking it to hang.
+        val stackStream = new java.io.ByteArrayOutputStream
+        e.printStackTrace(new java.io.PrintStream(stackStream))
+        b.setError(stackStream.toString())
+    }
+    b.build.toByteArray
   }
 
-  def handleCodeGeneratorRequest(request: CodeGeneratorRequest): CodeGeneratorResponse = {
-    val b = CodeGeneratorResponse.newBuilder
+  def handleCodeGeneratorRequest(
+    request: CodeGeneratorRequest,
+    b: CodeGeneratorResponse.Builder
+  ) = {
     ProtobufGenerator.parseParameters(request.getParameter) match {
       case Right(params) =>
         try {
@@ -73,18 +89,9 @@ object ExtraProtobufGenerator extends ProtocCodeGenerator {
         } catch {
           case e: GeneratorException =>
             b.setError(e.message)
-          case e: Throwable =>
-            // Yes, we want to catch _all_ errors and send them back to the
-            // requestor. Otherwise uncaught errors will cause the generator to
-            // die and the worker invoking it to hang.
-            val stackStream = new java.io.ByteArrayOutputStream
-            e.printStackTrace(new java.io.PrintStream(stackStream))
-            b.setError(stackStream.toString())
         }
       case Left(error) =>
         b.setError(error)
     }
-    b.build
   }
-
 }