fix: allow recursive BOMs as long as they don't recursively explode

[ankush]

This PR: #27157 blocked the creation of BOMs that where the item is present in any level of BOM. However, some use cases are simplified by using recursive BOM, hence adding this functionality back but only when item doesn't have BOM itself. This can be done by using "Do not explode": #29450

New logic:

• Parent BOM No. can never appear in BOM's tree
• Parent item code can appear as long as it's a child item without a BOM.

Unrelated changes:

• Show "New version" button (duplicating is not obvious to users)
• Fix issue with BOM no getting erased and reset with default.

closes #31159

[ankush]

Some unrelated test failing, probably due to translations caching... will fix separately 😅

[codecov]

Codecov Report

Merging #31175 (d7a7c47) into develop (4df76f3) will decrease coverage by 0.14%.
The diff coverage is 92.30%.

@@             Coverage Diff             @@
##           develop   #31175      +/-   ##
===========================================
- Coverage    63.09%   62.95%   -0.15%     
===========================================
  Files          986      986              
  Lines        67424    67422       -2     
===========================================
- Hits         42543    42445      -98     
- Misses       24881    24977      +96     

Impacted Files	Coverage Δ
erpnext/manufacturing/doctype/bom/bom.py	87.76% <91.66%> (+0.28%)	⬆️
...y_inspection_summary/quality_inspection_summary.py	93.54% <100.00%> (-0.21%)	⬇️
...unts/report/purchase_register/purchase_register.py	34.21% <0.00%> (-44.08%)	⬇️
...ext/accounts/report/balance_sheet/balance_sheet.py	36.36% <0.00%> (-21.82%)	⬇️
...e_purchase_register/item_wise_purchase_register.py	57.42% <0.00%> (-20.80%)	⬇️
...em_wise_sales_register/item_wise_sales_register.py	51.13% <0.00%> (-10.86%)	⬇️
...urity_shortfall/process_loan_security_shortfall.py	93.75% <0.00%> (-6.25%)	⬇️
erpnext/crm/doctype/prospect/prospect.py	55.22% <0.00%> (-1.50%)	⬇️
.../report/accounts_receivable/accounts_receivable.py	70.85% <0.00%> (-1.26%)	⬇️
...t/accounts/report/sales_register/sales_register.py	70.76% <0.00%> (-1.17%)	⬇️
... and 21 more