osmo-dev changes for OsmoBSCNAT

Hey Neels, and potentially other users of osmo-dev.git reading the ML,

since I'm using osmo-dev's net scripts to test OsmoBSCNAT while developing it, I submitted patches with significant changes that make testing easier/possible:

* config_mine is now a diff to config_2g3g * optionally build mobile + virtphy from osmocom-bb.git * optionally start BSC2, virtual BTS, virtual MS * all cmds can be overwritten in config_mine now, without modifying run.sh (e.g. to use valgrind, CMD_BSCNAT="valgrind osmo-bsc-nat")

Patches were submitted for review here: https://gerrit.osmocom.org/c/osmo-dev/+/27432/1

Related osmo-bsc-nat patches: https://gerrit.osmocom.org/c/osmo-bsc-nat/+/27461

Best, Oliver