[BUG] onedir - vendor system python packages

Description
note: follow on from https://saltstackcommunity.slack.com/archives/CNZKJMQ1E/p1691686473917269?thread_ts=1691617721.100279&cid=CNZKJMQ1E

some vendors supply custom os's with built in custom python packages (cisco, sonic (edgecore, broadcom), nimble, f5) which are not available from pypi etc AND have specific customizations in them for that specific build of the custom os/image.

those python packages make adjusting config/settings of these switches/sans/loadbalancers easier.
with classic packaging it was possible to import and use these python packages, with onedir it is not.

Setup
An example with sonic:

• install qemu on your system.
• download a sonic-vs.img (eg https://sonic-build.azurewebsites.net/api/sonic/artifacts?branchName=master&definitionId=1&artifactName=sonic-buildimage.vs&buildId=334542&target=target%2Fsonic-vs.img.gz)
• start the qemu image with an e1000 bridged nic (see https://github.com/sonic-net/SONiC/wiki/SONiC-on-virtual-machine-for-Windows#3-start-sonic-image for windows example qemu command)
• install onedir salt 3006.x inside the os (debian based)
• run salt's python interpreter, attempt to import any of the images python libs eg:

    from sonic_py_common.multi_asic import is_multi_asic
    from sonic_py_common.interface import get_interface_table_name, get_port_table_name
    from swsscommon import swsscommon
    from swsssdk import ConfigDBConnector
    from swsscommon.swsscommon import SonicV2Connector
    import utilities_common.cli as clicommon
    from config.config_mgmt import sonic_cfggen
    import click
    import config.main as sonic_config_main

this will fail as onedir cant access these on-system libs