diffoscope appears to repeatedly call programs with `--version`

Example: https://salsa.debian.org/reproducible-builds/diffoscope/-/blob/2d752e7ead892714bed836ee3d95e9500be06ee6/diffoscope/comparators/zip.py#L38-39

This is probably not that slow but it is hundreds to thousands of invocations and should probably be memoized. My suggestion is that for deterministic commands like --version, there could be a our_check_output that has a memoization cache by command line.