Catch Throwable in ExtraProtobufGenerator

[mbland]

Description

Added a catch case for Throwable in handleCodeGeneratorRequest. Part of #1482.

Motivation

Not catching this caused ProtoScalaPBRule workers to hang when building //test/... after bumping com_google_protobuf from 25.5 to 27.5. With this change, we can now see the error:

$ USE_BAZEL_VERSION=7.3.2 bazel build //test/...

ERROR: .../test/proto/BUILD:165:14:
  ProtoScalaPBRule test/proto/standalone_proto_strip_import_prefix_package_jvm_extra_protobuf_generator_scalapb.srcjar
  failed: (Exit 1): scalapb_worker failed:
  error executing ProtoScalaPBRule command
  (from target //test/proto:standalone_proto_strip_import_prefix_package)
  bazel-bin/src/scala/scripts/scalapb_worker
    ... (remaining 2 arguments skipped)

--jvm_extra_protobuf_generator_out: java.lang.NoSuchMethodError:
'java.lang.Object com.google.protobuf.DescriptorProtos$MessageOptions.getExtension(com.google.protobuf.GeneratedMessage$GeneratedExtension)'
    at scalapb.compiler.DescriptorImplicits$ExtendedMessageDescriptor.messageOptions(DescriptorImplicits.scala:532)
    at scalapb.compiler.DescriptorImplicits$ExtendedMessageDescriptor.sealedOneOfExtendsCount(DescriptorImplicits.scala:578)
    at scalapb.compiler.ProtoValidation.validateMessage(ProtoValidation.scala:107)
    at scalapb.compiler.ProtoValidation.$anonfun$validateFile$2(ProtoValidation.scala:17)
    at scalapb.compiler.ProtoValidation.$anonfun$validateFile$2$adapted(ProtoValidation.scala:17)
    at scala.collection.Iterator.foreach(Iterator.scala:943)
    at scala.collection.Iterator.foreach$(Iterator.scala:943)
    at scala.collection.AbstractIterator.foreach(Iterator.scala:1431)
    at scala.collection.IterableLike.foreach(IterableLike.scala:74)
    at scala.collection.IterableLike.foreach$(IterableLike.scala:73)
    at scala.collection.AbstractIterable.foreach(Iterable.scala:56)
    at scalapb.compiler.ProtoValidation.validateFile(ProtoValidation.scala:17)
    at scalapb.compiler.ProtoValidation.$anonfun$validateFiles$1(ProtoValidation.scala:10)
    at scalapb.compiler.ProtoValidation.$anonfun$validateFiles$1$adapted(ProtoValidation.scala:10)
    at scala.collection.immutable.Stream.foreach(Stream.scala:533)
    at scalapb.compiler.ProtoValidation.validateFiles(ProtoValidation.scala:10)
    at scalarules.test.extra_protobuf_generator.ExtraProtobufGenerator$.handleCodeGeneratorRequest(ExtraProtobufGenerator.scala:65)
    at scalarules.test.extra_protobuf_generator.ExtraProtobufGenerator$.run(ExtraProtobufGenerator.scala:47)
    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: .../test/proto/BUILD:165:14
  scala @//test/proto:standalone_proto_strip_import_prefix_package
  failed: (Exit 1): scalapb_worker failed:
  error executing ProtoScalaPBRule command
  (from target //test/proto:standalone_proto_strip_import_prefix_package)
  bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/src/scala/scripts/scalapb_worker
    ... (remaining 2 arguments skipped)

The fix for this is to bump ScalaPB jar versions to 1.0.0-alpha.1, which will come in a future change.