Migrate to bazelmod

Switch the BUILD from the in-tree gerrit_plugin macro (//tools/bzl)
to the bazlets gerrit_plugin.bzl macro, which auto-detects the build
mode and works both in-tree and standalone.

* gerrit_plugin: use plugin= instead of name=

Change-Id: I82b4608bd281d35d6cc2730827a4d01e3a12e091

BUILD

diff --git a/BUILD b/BUILD
index 0ec0321..35e817c 100644
--- a/BUILD
+++ b/BUILD
@@ -1,12 +1,12 @@
-load("//tools/bzl:plugin.bzl", "gerrit_plugin")
+load("@com_googlesource_gerrit_bazlets//:gerrit_plugin.bzl", "gerrit_plugin")
 
 gerrit_plugin(
-    name = "login-redirect",
     srcs = glob(["src/main/java/**/*.java"]),
     manifest_entries = [
         "Gerrit-PluginName: login-redirect",
         "Gerrit-HttpModule: com.googlesource.gerrit.plugins.loginredirect.LoginRedirectModule",
         "Implementation-Title: Login Redirect plug-in",
     ],
+    plugin = "login-redirect",
     resources = glob(["src/main/resources/**/*"]),
 )