refactor: validate SO and SI references in Delivery Notes (backport #40485)

[mergify]

Validation to prevent incomplete references of Sales Orders and Sales Invoices in Delivery Note. Either both, against_sales_order and so_detail should be set or both should be unset. Same applies for against_sales_invoice and si_detail.

Ex:

---

This is an automatic backport of pull request #40485 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 4d090bd has failed:

On branch mergify/bp/version-14-hotfix/pr-40485
Your branch is up to date with 'origin/version-14-hotfix'.

You are currently cherry-picking commit 4d090bd3b8.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/stock/doctype/delivery_note/delivery_note.py

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 4f396d3 has failed:

On branch mergify/bp/version-14-hotfix/pr-40485
Your branch is ahead of 'origin/version-14-hotfix' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 4f396d3049.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   erpnext/stock/doctype/delivery_note/test_delivery_note.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/selling/doctype/sales_order/test_sales_order.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[frappe-pr-bot]

🎉 This PR is included in version 14.65.4 🎉

The release is available on GitHub release

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