List all the packages and their versions in benchmark log

I cannot find an easy way to see in the log what packages were installed for a given benchmark run and what versions. Would be nice to have this info. A simple `pip freeze` would suffice for now.

xref https://github.com/astropy/astropy/pull/16296#issuecomment-2064654606

Start by locating how benchmark runs produce their logs and where the runtime environment is recorded. Capture the installed Python packages and versions for each run, using the suggested pip freeze approach, then run a benchmark and verify that the log contains this information.

Written by the indexing model from the issue text.