feat: Custom branch and editable flags for dev deployments

[k-anshul]

closes https://linear.app/rilldata/issue/PLAT-344/support-user-specified-branch-for-dev-deployments Also fixes the issue that editing branch does not change deployment's branch - only used for display purposes.

Checklist:

• [ ] Covered by tests
• [x] Ran it and it works as intended
• [x] Reviewed the diff before requesting a review
• [x] Checked for unhandled edge cases
• [x] Linked the issues it closes
• [ ] Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• [ ] Intend to cherry-pick into the release branch
• [x] I'm proud of this work!