test: add spanner executor v1

[parthea]

For testing purposes
Googlers see cl/634783571 b/325234697

1. In order to avoid a conflict between protobuf stubs and proto-plus, run the following commands to change the protobuf package name in the proto-plus library

sed -i -e 's/google.spanner.v1\"/google.spanner.v1.gapic_generated\"/g' google/cloud/spanner_v1/types/*.py

sed -i -e 's/google.spanner.admin.database.v1\"/google.spanner.admin.database.v1.gapic_generated\"/g' google/cloud/spanner_admin_database_v1/types/*.py

sed -i -e 's/google.spanner.admin.instance.v1\"/google.spanner.admin.instance.v1.gapic_generated\"/g' google/cloud/spanner_admin_instance_v1/types/*.py

2. Re-install the spanner library

pip install .

3. Run

cd test_proxy/protos
python3 cloud_executor_server.py 

You should see

(py392) partheniou@partheniou-vm-3:~/git/python-spanner/test_proxy/protos$ python3 cloud_executor_server.py 
Server started, listening on 50055

4. Run the test suite. For example,

partheniou@partheniou-vm-3:~/git/spanner_test$ go run tests/client_main_mini.go 
2024/06/22 17:36:20 Getting feature for point
2024/06/22 17:36:20 Got output 0, <nil>
2024/06/22 17:36:25 client.RouteChat: stream.Send(action_id:6  action:{query:{sql:"SELECT name, user_id as id FROM Users ORDER BY name DESC"}}) failed: EOF
exit status 1