Set _APPSIGNAL_PROCESS_NAME config

[tombruijn]

To do

• Figure out how to get the Python process name
• Set it as _APPSIGNAL_PROCESS_NAME

[tombruijn]

Looks like there's no $PROCESS_NAME like global or env var in Python from which we can fetch it. A lot of links point to https://pypi.org/project/psutil/, but for such a small thing I don't know if we should add a dependency with all that functionality right now.

In the end it fetches it from the proc dir for Linux, uses sysctl for macOS, and we don't support Windows. Not sure about FreeBSD.

I suggest we leave it for a little later. If it was small it was a nice addition, if it's a lot of work/dependency discussion let's postpone it.

[unflxw]

I'd be okay with adding the dependency. 🤷