[1/7] feat(submit:phabricator): pass `--allow-untracked` to `arc`

[arxanas]

Stack:

• https://github.com/arxanas/git-branchless/pull/1353
• https://github.com/arxanas/git-branchless/pull/1354
• https://github.com/arxanas/git-branchless/pull/1355
• https://github.com/arxanas/git-branchless/pull/1356
• https://github.com/arxanas/git-branchless/pull/1202
• https://github.com/arxanas/git-branchless/pull/1357
• https://github.com/arxanas/git-branchless/pull/1358

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feat(submit:phabricator): pass --allow-untracked to arc

This is normal when moving back and forth between commits that change a .gitignore: there might be files which are untracked in one commit but ignored in another.