fix(requests): resolve lint issues E505/E510/E605/E610/E615
- E505: add h2_conpool_handler.mli with abstract h2_state type
- E510: add log source to bin/ocurl.ml
- E605: recreate test_one.ml as proper unit tests for One module
- E610: add lib/h2/h2_types.ml to satisfy test_h2_types.ml
- E615: include Test_one and Test_response suites in test.ml