This resolves #104

• add a new custom "dependabot" that checks for a new ldmx-sw release weekly and update the testing versions accordingly (replace the latest testing version if it is a patch release, append a new latest testing version otherwise)
• change backwards compatibility patches to be patch files from git diff rather than scripts
• have the AMD build happen on GitHub runners? <- not sure if I want to make this work but it is technically feasible
• use denv for test building ldmx-sw
• use just as well so we respect the recipes in the justfile and don't have to update stuff here when testing

I did test runs of ./ci/test-ldmx-sw locally and it works. With the other builds happening right now (and the layer caching being broken I think?), the CI tests on GitHub were cancelled after waiting too long to be run.