Add Git information to cargo-gpu's --version CLI subcommand

[Steveplays28]

• Added a build-time dependency on vergen-gix

Old:

$ cargo-gpu --version
cargo-gpu 0.10.0-alpha.1

New:

$ cargo-gpu --version
cargo-gpu 0.10.0-alpha.1 (2e5047eb4b; 2026-06-28)

I left the short version subcommand (-V) unchanged.

[nazar-pc]

It is just my opinion, but it seems really wasteful to add such a massive dependency tree for such a tiny feature.

You essentially added more than 1000 lines of dependencies just to obtain VERGEN_GIT_COMMIT_DATE environment variable, which doesn't make sense to me. Everything else was already there.

Adding commit hash is a single line change instead of current +1346 -80, adding date is a bit more than that, but still less than what this PR does.