Add a script that maintains a linux repository in one place on jenkins nodes, so we need less git clones from git.kernel.org and less disk space. All jobs that need a kernel tree can now clone the relevant branch directly from the jenkins node.
Follow up patches will add a jenkins job that runs the script daily and adjust the existing jobs to make use of this instead of doing their own clones.
Currently this script produces a 396M bare git repository.
The debian 10 repository has been officially disabled: https://osmocom.org/news/308
However we just re-enabled a subset of the packages, osmo-gbproxy + dependencies, because currently they are relevant for a customer. Adjust the repo-install-test to deal with this subset of packages for debian 10 to fix that it is currently failing.
I have verified that repo-install-test works with this change for debian 10, 11 and 12. It currently doesn't run for debian 13 yet (OS#6934).
