Rework intra line diff to interrupt threads instead of killing them

Now that MyersDiff is interruptible[1], interrupt threads instead of
killing them when MyersDiff goes into infinite loop.

Replace IntraLineWorkerPool that was created to allow killing threads by
a standard CachedThreadPool.

[1] https://git.eclipse.org/r/44041

Change-Id: I39ceef66f503fb9f0b6036fc32b671818772c258

gerrit-server/src/main/java/com/google/gerrit/server/patch/DiffExecutorModule.java

@@ -0,0 +1,39 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.patch;
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import com.google.inject.AbstractModule;
+import com.google.inject.Provides;
+import com.google.inject.Singleton;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+/** Module providing the {@link DiffExecutor}. */
+public class DiffExecutorModule extends AbstractModule {
+
+  @Override
+  protected void configure() {
+  }
+
+  @Provides
+  @Singleton
+  @DiffExecutor
+  public ExecutorService createDiffExecutor() {
+    return Executors.newCachedThreadPool(new ThreadFactoryBuilder()
+        .setNameFormat("Diff-%d").setDaemon(true).build());
+  }
+}