Add options to control HTTPX resource limits

[carl-baillargeon]

Currently, asynceapi uses the default resource limits settings of HTTPX which comes with default max_connections set to 100.

In ANTA, we should be able to control these resource limits or at least the max_connections settings. Since each connection uses a file description and consumes memory, that could become problematic at a high number of devices as it adds a lot of overhead for the ANTA runner.

We can also see better performance when running with max_connections set to 5-10 using this script on Python 3.12.