Add BLAKE3 hasher to vfs

This PR adds the Blake3Hasher and Blake3HashFunction classes to vfs and
makes them available under the flag --digest_function=BLAKE3.

This is a partial commit for #18658.

Closes #18784.

PiperOrigin-RevId: 550525978
Change-Id: Iedc0886c51755585d56b4d8f47676d3be5bbedba
diff --git a/BUILD b/BUILD
index 84c15b6..0540bb8 100644
--- a/BUILD
+++ b/BUILD
@@ -96,6 +96,7 @@
 pkg_tar(
     name = "bootstrap-jars",
     srcs = [
+        "@blake3",
         "@com_google_protobuf//:protobuf_java",
         "@com_google_protobuf//:protobuf_java_util",
         "@com_google_protobuf//:protobuf_javalite",