Move Truth rules to a subdirectory of lib

The list of supported Truth extensions is only going to grow.

Change-Id: Ic67a9df6a7548d964fc10b13c10b6db1c96e514e

java/com/google/gerrit/acceptance/BUILD

@@ -77,8 +77,6 @@ java_library2(
         "//java/com/google/gerrit/server/project/testing:project-test-util",
         "//java/com/google/gerrit/testing:gerrit-test-util",
         "//lib:jimfs",
-        "//lib:truth",
-        "//lib:truth-java8-extension",
         "//lib/auto:auto-value",
         "//lib/auto:auto-value-annotations",
         "//lib/httpcomponents:fluent-hc",
@@ -88,6 +86,8 @@ java_library2(
         "//lib/jgit/org.eclipse.jgit.junit:junit",
         "//lib/log:impl_log4j",
         "//lib/log:log4j",
+        "//lib/truth",
+        "//lib/truth:truth-java8-extension",
         "//prolog:gerrit-prolog-common",
     ],
     visibility = ["//visibility:public"],