Bazel: Replace PACKAGE_NAME constant with package_name() function

PACKAGE_NAME was deprecated in favor of package_name() function and is
going to be removed in future Bazel releases. Moreover Bazel is trying
to set --incompatible_package_name_is_a_function=true per default to
enforce Bazel users to stop using it: [1].

[1] bazelbuild/bazel#5827

Change-Id: Ida9f63a4a5763f12461795ef94aaf3d2ed9015d0

tools/js.bzl

@@ -426,7 +426,7 @@ _bundle_rule = rule(
 
 def bundle_assets(*args, **kwargs):
     """Combine html, js, css files and optionally split into js and html bundles."""
-    _bundle_rule(*args, pkg = PACKAGE_NAME, **kwargs)
+    _bundle_rule(*args, pkg = native.package_name(), **kwargs)
 
 def polygerrit_plugin(name, app, srcs = [], assets = None, **kwargs):
     """Bundles plugin dependencies for deployment.
@@ -447,7 +447,7 @@ def polygerrit_plugin(name, app, srcs = [], assets = None, **kwargs):
         name = name + "_combined",
         app = app,
         srcs = srcs if app in srcs else srcs + [app],
-        pkg = PACKAGE_NAME,
+        pkg = native.package_name(),
         **kwargs
     )