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.
This work aims to make Linux builds faster to make https://github.com/ooni/probe/issues/2249 more convenient. Since those builds runs inside Docker, the problem to solve here is to save/restore the Go caches notwithstanding Docker. Because Docker runs as root, we need to modify the build a bit to run as a normal user. Otherwise, we will not be able to save the Go cache using actions/cache@v3. (Other approaches such as using `sudo` are possible but running the build as an unprivileged user actually looks cleaner, so I chose to do that.) While there, add a `.editorconfig`.
