Closes https://github.com/ooni/probe/issues/2334.
While there, reinstate integration tests, which were also lost in a previous refactoring. However, only run those tests for linux/amd64 because we can be confident that the Go compiler is WAI for all archs we support.
While there, always use bash for running end-to-end tests.
H/T @ainghazal for discovering and reporting this bug.
