Move TimestampGranularityMonitor to CommandEnvironment.

This is one of the last pieces of state in BlazeRuntime that isn't safe to
share across command invocations.

--
MOS_MIGRATED_REVID=117910631
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java b/src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java
index 0f2fb63..cf8f668 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java
@@ -568,7 +568,7 @@
 
   @VisibleForTesting
   static FileValue fileValueFromArtifactFile(ArtifactFile file,
-      @Nullable FileStatusWithDigest statNoFollow, TimestampGranularityMonitor tsgm)
+      @Nullable FileStatusWithDigest statNoFollow, @Nullable TimestampGranularityMonitor tsgm)
       throws IOException {
     Path path = file.getPath();
     RootedPath rootedPath =