[EDITOR-527] E2E testing infrastructure

[zmoog]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• Tests for the changes have been added (for bug fixes / features)

• What kind of change does this PR introduce?

add e2e test infrastructure based on arduino-cli's one (using python and pytest)

• What is the current behavior?

• What is the new behavior?

test infrastructure is added, also to CI

• Does this PR introduce a breaking change?

no

• Other information:

• add test infra
• add in taskfile
• develop some basic test (meaningfully tests will be added later along the way)
• integrate in the CI

[umbynos]

apparently triggering the \update on the cli version of the agent causes it to update to the GUI version 😢 thus causing the CI to fail (the runners do not have a GUI).
We need to fix this behavior

[umbynos]

============================= test session starts ==============================
platform darwin -- Python 3.9.1, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: /Users/runner/work/arduino-create-agent/arduino-create-agent, configfile: pyproject.toml
collected 6 items

test/test_certs.py ..                                                    [ 33%]
test/test_info.py .                                                      [ 50%]
test/test_update.py ss                                                   [ 83%]
test/test_v2.py .                                                        [100%]

========================= 4 passed, 2 skipped in 2.54s =========================

🥳
Although the test_update will be skipped for now: it has some weird behavior:

• test_update_shutdown tries to test if the agent returns 200 along with a json(/update endpoint does not work properly on macos #608) shuts down correctly (we check this behavior waiting for the process to exit) -> there is a problem in this approach: the pytest fixture running the agent, by default, tries to kill it at the end of the test (but in this case is already killed)
• test_latest_version tries to check if the version started after the update is the latest one (by checking the version number available on agent-version.json on s3). This test is correct, but the problem comes from the fact that another fixture is required: two instances of the agent will be running at the same time. One generated by the update (we do not have a way to kill it) and one generated by the fixture. Which will be the one responding to the /info? Hard to guess.

Another important thing to point out: the agent has been updated at this point: we need to rebuild it, otherwise the version under test will be the latest one, and not the one we are developing.

[umbynos]

it would be good to dynamically check the port from (8991 to 9000)

[umbynos]

@zmoog approved 🏁