Copy gwtorm dependencies into core repo

This is the minimal set of files from gwtorm that are still needed by
Gerrit core. The long term plan is to migrate away from these, for
example by revamping our exception hierarchy (I9c8fac5f) and converting
the legacy mutable gwtorm-based types to immutable AutoValues.

In the short term, copying these files into core allows us to remove a
bunch of unused class files from the war, and prevents new dependencies
from creeping in. This change should be viewed as a starting point of
the larger project to eliminate gwtorm, not an end in itself.

Files copied from:
https://gerrit.googlesource.com/gwtorm/+/de62a8902ade3239e4a2db105bb24e4561e34df3

The whole gwtorm repo is under the same AOSP umbrella as Gerrit core, so
it's all under the same CLA and can be copied between repos on the
Gerrit hosts without any change to the license.

Change-Id: I0f09ed399180bc132fb0a28be07944b4aa9fe4a0

javatests/com/google/gerrit/server/update/BUILD

@@ -12,8 +12,8 @@ junit_tests(
         "//java/com/google/gerrit/server/schema",
         "//java/com/google/gerrit/server/util/time",
         "//java/com/google/gerrit/testing:gerrit-test-util",
+        "//java/com/google/gwtorm",
         "//lib:guava",
-        "//lib:gwtorm",
         "//lib/guice",
         "//lib/jgit/org.eclipse.jgit:jgit",
         "//lib/jgit/org.eclipse.jgit.junit:junit",