chore: enable rust codepath on CI (#6449)
### Description
This PR switches to use the Rust codepath for turborepo CI.
Part of this PR switches our Windows usage to use GitBash instead of
Powershell for invoking `turbo`. This isn't ideal, but it allows us to
start dogfooding.
### Testing Instructions
Our existing CI should pass. We should eagerly revert if an issue is
discovered.
Closes TURBO-1665
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Co-authored-by: Chris Olszewski <Chris Olszewski>
