Remove xforms table from database, refactor project creation

[spwoodcock]

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation
• 🧑‍💻 Refactor
• ✅ Test
• 🤖 Build or CI
• ❓ Other (please specify)

Describe this PR

• Simplified logic during project creation.
• Added migration to remove xforms table, replacing with projects.odk_form_id an projects.xlsform_content.
• Previously I thought we might have multiple xlsforms per project, but it's become clear that this is not actually desirable. Instead we just want to map multiple features via the same form; functionality we have almost finished adding.
• I also removed all remaining XML manipulation, in favour of the new Pandas XLSX editing we have added in osm-fieldwork. I could remove the defusedxml dependency too.

Checklist before requesting a review

• 📖 Read the FMTM Contributing Guide: https://github.com/hotosm/fmtm/blob/main/CONTRIBUTING.md
• 📖 Read the HOT Code of Conduct: https://docs.hotosm.org/code-of-conduct
• 👷‍♀️ Create small PRs. In most cases, this will be possible.
• ✅ Provide tests for your changes.
• 📝 Use descriptive commit messages.
• 📗 Update any related documentation and include any relevant screenshots.

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[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ PanicException: range end index 2 out of range for slice of length 1 app.central.central_crud in append_fields_to_us... View Issue

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Not sure if this is useful / has been fixed already @Sujanadh