Combined output for facts with custom success codes

Problem

Currently, when getting facts, only the stdout is returned in case of success. Now beccause we support success_exit_codes in fact fetching like this after #755:

from pyinfra import facts, host

fact = host.get_fact(
    facts.server.Command,
    "somefailingcommand",
    success_exit_codes=[0, 27, 55])

# Now fact only contains stdout and won't contain stderr. 

The fact only has stdout but becuse the "succuess" was kind hacked by suggesting a list of OK codes, the only stdout is returned but the actualy output of the command is on stderr which is igonred.

Possible solutions

One possible solution is to add something like returned_combined_output kind of keyword argument that combines stdout and stderr regardless of the status code. That would require changes in pyinfra itself.

Other workaround is to issue your shell commands like this by redirecting and combining stdout and stderr together:

somefailingcommand 2>&1

I am not sure, open to ideas and suggestions.

Start by tracing facts.server.Command and the success_exit_codes behavior introduced after #755. Decide how combined stdout and stderr should be exposed when a custom success code is accepted. Done means the chosen behavior is implemented and covered for successful commands whose output is on stderr.