Extract ActionContext to a top-level class

PiperOrigin-RevId: 159423459
diff --git a/src/main/java/com/google/devtools/build/lib/exec/FilesetActionContextImpl.java b/src/main/java/com/google/devtools/build/lib/exec/FilesetActionContextImpl.java
index a234e8f..d21b270 100644
--- a/src/main/java/com/google/devtools/build/lib/exec/FilesetActionContextImpl.java
+++ b/src/main/java/com/google/devtools/build/lib/exec/FilesetActionContextImpl.java
@@ -15,8 +15,8 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import com.google.devtools.build.lib.actions.ActionContext;
 import com.google.devtools.build.lib.actions.ExecutionStrategy;
-import com.google.devtools.build.lib.actions.Executor.ActionContext;
 import com.google.devtools.build.lib.events.Reporter;
 import com.google.devtools.build.lib.rules.fileset.FilesetActionContext;
 import java.util.concurrent.LinkedBlockingQueue;