CI: use git-lfs fork for git_lfs_probe.py

[redsun82]

This switches the fragile git_lfs_probe.py functionality out for a fork of git-lfs providing that functionality.

For the moment, the fork is located at https://github.com/dsp-testing/codeql-git-lfs, and it contains a new git-lfs ls-urls command reusing git-lfs authentication and url fetching, as well as a modified release.yml workflow and upload script for creating special releases there.

Long term, we might want to polish that into something upstreamable. If that takes too long, or if we can't rely on developers having an updated git-lfs, then we might think about moving the dsp-testing fork over to a github/codeql-git-lfs fork (I don't have permissions to do that.

[criemen]

or if we can't rely on developers having an updated git-lfs

I think we can (always?) think about bundling a lfs binary somewhere (in lfs itself in the internal repo? a public release somewhere?) to work around that requirement, and I do generally like the idea of upstreaming these changes.