Prefetch inputs before acquiring the resource and sending Executing event.

prefetchInputs could wait for network I/Os to download all the inptus for this local action which might take a long time. It is possiable that local actions acqure resource and then wait for the network I/Os which is a waste.

The prefetch is also moved before sending Executing event so that the UI will display the action is being prepared instead of running. i.e.

```
[Prepa] Linking xxx
```

instead of

```
Linking xxx
```

when prefetching inputs for the action.

PiperOrigin-RevId: 481874944
Change-Id: I5cd9d379d3ddc68ddf444d4c0ebce5f1ae3ef905

Author: coeuvre

src/main/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunner.java

@@ -141,6 +141,9 @@ public SpawnResult exec(Spawn spawn, SpawnExecutionContext context)
         spawn.getEnvironment(),
         context.getFileOutErr(),
         xattrProvider);
+    if (Spawns.shouldPrefetchInputsForLocalExecution(spawn)) {
+      context.prefetchInputsAndWait();
+    }
     spawnMetrics.addSetupTime(setupTimeStopwatch.elapsed());
 
     try (SilentCloseable c =
@@ -351,12 +354,6 @@ private SpawnResult start()
             .build();
       }
 
-      if (Spawns.shouldPrefetchInputsForLocalExecution(spawn)) {
-        stepLog(INFO, "prefetching inputs for local execution");
-        setState(State.PREFETCHING_LOCAL_INPUTS);
-        context.prefetchInputsAndWait();
-      }
-
       spawnMetrics.setInputFiles(spawn.getInputFiles().memoizedFlattenAndGetSize());
       Stopwatch setupTimeStopwatch = Stopwatch.createStarted();
       for (ActionInput input : spawn.getInputFiles().toList()) {

src/main/java/com/google/devtools/build/lib/remote/RemoteSpawnCache.java

@@ -157,10 +157,10 @@ public CacheHandle lookup(Spawn spawn, SpawnExecutionContext context)
       }
     }
 
-    context.report(SPAWN_EXECUTING_EVENT);
-
     context.prefetchInputsAndWait();
 
+    context.report(SPAWN_EXECUTING_EVENT);
+
     if (shouldUploadLocalResults) {
       return new CacheHandle() {
         @Override

src/main/java/com/google/devtools/build/lib/sandbox/AbstractSandboxSpawnRunner.java

@@ -87,14 +87,23 @@ public final SpawnResult exec(Spawn spawn, SpawnExecutionContext context)
       throws ExecException, InterruptedException {
     ActionExecutionMetadata owner = spawn.getResourceOwner();
     context.report(SpawnSchedulingEvent.create(getName()));
-    try (ResourceHandle ignored =
-        resourceManager.acquireResources(
-            owner,
-            spawn.getLocalResources(),
-            context.speculating() ? ResourcePriority.DYNAMIC_STANDALONE : ResourcePriority.LOCAL)) {
-      context.report(SpawnExecutingEvent.create(getName()));
-      SandboxedSpawn sandbox = prepareSpawn(spawn, context);
-      return runSpawn(spawn, sandbox, context);
+
+    try {
+      try (SilentCloseable c = Profiler.instance().profile("context.prefetchInputs")) {
+        context.prefetchInputsAndWait();
+      }
+
+      try (ResourceHandle ignored =
+          resourceManager.acquireResources(
+              owner,
+              spawn.getLocalResources(),
+              context.speculating()
+                  ? ResourcePriority.DYNAMIC_STANDALONE
+                  : ResourcePriority.LOCAL)) {
+        context.report(SpawnExecutingEvent.create(getName()));
+        SandboxedSpawn sandbox = prepareSpawn(spawn, context);
+        return runSpawn(spawn, sandbox, context);
+      }
     } catch (IOException e) {
       FailureDetail failureDetail =
           createFailureDetail(
@@ -129,9 +138,6 @@ private SpawnResult runSpawn(
         sandbox.createFileSystem();
       }
       FileOutErr outErr = context.getFileOutErr();
-      try (SilentCloseable c = Profiler.instance().profile("context.prefetchInputs")) {
-        context.prefetchInputsAndWait();
-      }
 
       SpawnResult result;
       try (SilentCloseable c = Profiler.instance().profile("subprocess.run")) {