Slow local end-to-end tests execution if the host is not connected to internet

[Artifizer]

Every test takes several seconds if the host is not connected to the internet:

$ make all
...
Successfully connected to GTS server at http://127.0.0.1:8000/entities
======================================================================== test session starts ========================================================================
platform darwin -- Python 3.9.6, pytest-8.4.2, pluggy-1.5.0 -- /Users/alexa/.pyenv/versions/3.9.6/bin/python3.9
hypothesis profile 'default'
metadata: {'Python': '3.9.6', 'Platform': 'macOS-15.5-arm64-arm-64bit', 'Packages': {'pytest': '8.4.2', 'pluggy': '1.5.0'}, 'Plugins': {'cov': '6.0.0', 'flake8': '1.3.0', 'asyncio': '1.2.0', 'html': '3.2.0', 'hypothesis': '6.135.24', 'metadata': '3.1.1', 'tavern': '2.12.0', 'anyio': '4.8.0', 'schemathesis': '4.0.4', 'mock': '3.14.0', 'subtests': '0.14.2'}}
rootdir: /Users/alexa/git/github/gts-rust/.gts-spec/tests
configfile: pytest.ini
plugins: cov-6.0.0, flake8-1.3.0, asyncio-1.2.0, html-3.2.0, hypothesis-6.135.24, metadata-3.1.1, tavern-2.12.0, anyio-4.8.0, schemathesis-4.0.4, mock-3.14.0, subtests-0.14.2
asyncio: mode=strict, debug=False, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
collected 314 items                                                                                                                                                 

.gts-spec/tests/test_op10_query_execution.py::TestCaseTestOp10Query_ExactMatch::test_start PASSED                                                             [  0%]
.gts-spec/tests/test_op10_query_execution.py::TestCaseTestOp10Query_InvalidQuery1::test_start PASSED                                                          [  0%]
.gts-spec/tests/test_op10_query_execution.py::TestCaseTestOp10Query_InvalidQuery2::test_start PASSED                                                          [  0%]
.gts-spec/tests/test_op10_query_execution.py::TestCaseTestOp10Query_InvalidQuery3::test_start PASSED                                                          [  1%]