Removes git sandbox feature

The reason is essentially:
- write access to a `.git` dir can be trivially escalated to unsandboxed
access
- therefore, it is misleading to offer git access separate from
unsandboxed access
- instead, we encourage the model to use `--no-optional-locks` to avoid
needing write access to `git status`, etc.


Adds sandboxing to fetch tool
 


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Release Notes:

- N/A or Added/Fixed/Improved ...

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Co-authored-by: zed-zippy[bot] <234243425+zed-zippy[bot]@users.noreply.github.com>