Describe the bug

Recently in this PR the --install option was added to the upgrade command.
Unfortunately this doesn't seem to respect the --system-site-packages option.

How to reproduce

When using upgrade --install the --system-site-packages option isn't respected:

❯ pipx upgrade --install --system-site-packages pycowsay
❯ grep system $HOME/.local/share/pipx/venvs/pycowsay/pyvenv.cfg
include-system-site-packages = false

Comparison with the install command, where it works correctly:

❯ pipx install --system-site-packages pycowsay
❯ grep system $HOME/.local/share/pipx/venvs/pycowsay/pyvenv.cfg
include-system-site-packages = true
command = /usr/bin/python3 -m venv --without-pip --system-site-packages /home/sadamczyk/.local/share/pipx/venvs/pycowsay

Expected behavior

The upgrade --install command should handle the --system-site-packages option just like the install command does.

Investigation

Looking through the code, the --system-site-packages option seems to be passed to the install command in the venv_args variable from the get_venv_args function:

But venv_args is only passed to the run, install and install-all commands

It might be enough to add the required function arguments so that the venv_args from the main.py can be passed through all the way to the install call here: