Enhancement: Capture the `distrib-rl` version and project git details in the checkpoint

[some-rando-rl]

In order to maintain reproducibility, checkpoints should capture the version of distrib-rl that produced them.

Similarly when distrib-rl is executed either from its own git repo or as part of a project that is contained within a git repo, the checkpoint should include details about the state of the repo, such as the origin, branch name, commit hash, whether the working directory is clean, and the current working directory diff in the case when the working directory is not clean.

Note: this will likely involve changing the checkpoint format over to something other than .npy exports.