feat: item-wise negative stock setting

[ankush]

Change:

• On each item you can now specify if it's allowed to go negative DESPITE disabling negative stock globally.

closes #29636

TODO:

• docs
• check and fix the remaining references stock settings field. (some are actually unused, so might drop them)

docs: https://docs.erpnext.com/docs/v14/user/manual/en/stock/item#33-inventory

[codecov]

Codecov Report

Merging #29761 (5f81bec) into develop (77be982) will increase coverage by 6.98%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop   #29761      +/-   ##
===========================================
+ Coverage    52.07%   59.06%   +6.98%     
===========================================
  Files         1111     1112       +1     
  Lines        69408    69577     +169     
===========================================
+ Hits         36146    41093    +4947     
+ Misses       33262    28484    -4778     

Impacted Files	Coverage Δ
...rpnext/accounts/doctype/pos_invoice/pos_invoice.py	73.19% <100.00%> (+1.28%)	⬆️
erpnext/stock/doctype/stock_entry/stock_entry.py	81.08% <100.00%> (+12.40%)	⬆️
erpnext/stock/stock_ledger.py	86.54% <100.00%> (+4.00%)	⬆️
...eport/item_variant_details/item_variant_details.py	31.32% <0.00%> (-56.63%)	⬇️
...tch_item_expiry_status/batch_item_expiry_status.py	69.23% <0.00%> (-25.00%)	⬇️
...wise_balance_history/batch_wise_balance_history.py	68.96% <0.00%> (-24.14%)	⬇️
...xt/stock/report/stock_analytics/stock_analytics.py	80.19% <0.00%> (-12.88%)	⬇️
...rial_no_valuation/incorrect_serial_no_valuation.py	85.96% <0.00%> (-10.53%)	⬇️
...t/accounts/report/sales_register/sales_register.py	73.33% <0.00%> (-7.28%)	⬇️
...pnext/accounts/report/gross_profit/gross_profit.py	82.49% <0.00%> (-6.23%)	⬇️
... and 213 more