Moves unittests to root folder and adds github action to run unit tests. (#72)

* Move unit tests to root package.

* Adds deps to "test" extra, and mark two broken tests in tests/unittests/auth/test_auth_handler.py

* Adds github workflow

* minor fix in lite_llm.py for python 3.9.

* format pyproject.toml

tests/unittests/tools/__init__.py

@@ -0,0 +1,14 @@
+# Copyright 2025 Google LLC
+#
+# 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.
+