Add license blurb to bzl_library_test.bzl and move blurb-less test data files to testdata subdir (#503)

Required by internal license checker.

tests/bzl_library/BUILD

@@ -3,17 +3,17 @@ load(":bzl_library_test.bzl", "bzl_library_test")
 
 filegroup(
     name = "a",
-    srcs = ["a.bzl"],
+    srcs = ["testdata/a.bzl"],
 )
 
 bzl_library(
     name = "b",
-    srcs = ["b.bzl"],
+    srcs = ["testdata/b.bzl"],
 )
 
 bzl_library(
     name = "c",
-    srcs = ["c.bzl"],
+    srcs = ["testdata/c.bzl"],
     deps = [
         ":a",
         ":b",
@@ -22,11 +22,11 @@ bzl_library(
 
 bzl_library_test(
     name = "bzl_library_test",
-    expected_srcs = ["c.bzl"],
+    expected_srcs = ["testdata/c.bzl"],
     expected_transitive_srcs = [
-        "a.bzl",
-        "b.bzl",
-        "c.bzl",
+        "testdata/a.bzl",
+        "testdata/b.bzl",
+        "testdata/c.bzl",
     ],
     target_under_test = ":c",
 )

tests/bzl_library/bzl_library_test.bzl

@@ -1,3 +1,17 @@
+# Copyright 2024 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 """Unit tests for bzl_library"""
 
 load("//:bzl_library.bzl", "StarlarkLibraryInfo")

tests/bzl_library/testdata/c.bzl

@@ -1,6 +1,6 @@
 """c.bzl, standin' on the shoulder of giants"""
 
-load(":a.bzl", "A")
-load(":b.bzl", "B")
+load(":testdata/a.bzl", "A")
+load(":testdata/b.bzl", "B")
 
 C = A + B