Adding support for SHA256 for remote execution. Switch remote execution to use
the currently defined hash function for blobs. Some refactoring. Adding an option to set the hash function in the remote worker, defaulting to the current behavior (unfortunately it is a build option, have not found a clean way to specify it at runtime).

BUG=62622420
TESTED=remote worker
RELNOTES: none
PiperOrigin-RevId: 159473116
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
index 5150961..2bd2ba9 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
@@ -822,7 +822,7 @@
       @Nullable
       @Override
       public byte[] getDigest() throws IOException {
-        return path.getMD5Digest();
+        return path.getDigest();
       }
 
       @Override