* refactor(httpx): use mocks to implement tests While there, make sure no test depends on external services by replacing such tests with httptest. See https://github.com/ooni/probe/issues/1951. * fix(httpx): ensure we honour the context
* refactor(httpx): use mocks to implement tests While there, make sure no test depends on external services by replacing such tests with httptest. See https://github.com/ooni/probe/issues/1951. * fix(httpx): ensure we honour the context