refactor!: dynamically compute bom_level (backport #29522)

[mergify]

This is an automatic backport of pull request #29522 done by Mergify.
Cherry-pick of 157b4b3 has failed:

On branch mergify/bp/version-13-hotfix/pr-29522
Your branch is up to date with 'origin/version-13-hotfix'.

You are currently cherry-picking commit 157b4b33fe.
  (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/manufacturing/doctype/bom/bom.json
	modified:   erpnext/manufacturing/doctype/production_plan/production_plan.py
	modified:   erpnext/manufacturing/doctype/production_plan_sub_assembly_item/production_plan_sub_assembly_item.json
	modified:   erpnext/manufacturing/report/bom_explorer/bom_explorer.py
	modified:   erpnext/manufacturing/report/production_plan_summary/production_plan_summary.py
	deleted:    erpnext/patches/v13_0/update_level_in_bom.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/manufacturing/doctype/bom/bom.py
	both modified:   erpnext/patches.txt

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

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