fix: disable console history in tests

[ghost]

What I did

Prevents IPython from spawning history collection threads when running the test suite

fixes: #881

How I did it

Add an auto-used fixture to patch an APE_TESTING environment variable in while testing. The IPython embedded instance launches with history disabled if this environment variable is set.

How to verify it

If the tests weren't failing from "too many open files", you can change the soft limit on your machine with this.

$ ulimit -n  # check current value so you can restore it later
...
$ ulimit -Sn 256  # set value to what was default in #881's repro steps
$ pytest tests/integration

This should produce a failure without these changes

Checklist

• All changes are completed
• New test cases have been added
• Documentation has been updated

[ghost]

This seemed to only arise from running the test suite, so I opted to change up enabling the fault handler only when we aren't testing (i.e. have the test env set)

[ghost]

Is it safe to assume an empty config when not environ.get("APE_TESTING") or should I have two separate paths and not provide the config kwarg at all if the env var isn't set?

[fubuloubu]

Very good contribution!