fix: Advance paid amount in orders

[deepeshgarg007]

When two partial payment entries are made simultaneously against a single order using two separate requests, both requests try to update the Advance Paid amount simultaneously and create a race condition.

Since both the requests read the previous advance amount as 0 the amount of the request which updates the value later is only seen rather than the sum of both entries.

Added a for_update flag to resolve the issue

[codecov]

Codecov Report

Merging #32642 (0567d2e) into develop (633c2a2) will decrease coverage by 0.27%.
The diff coverage is 88.23%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #32642      +/-   ##
===========================================
- Coverage    63.99%   63.72%   -0.28%     
===========================================
  Files          817      816       -1     
  Lines        58228    58310      +82     
===========================================
- Hits         37264    37156     -108     
- Misses       20964    21154     +190     

Impacted Files	Coverage Δ
erpnext/regional/united_arab_emirates/setup.py	100.00% <ø> (ø)
...ctype/stock_reconciliation/stock_reconciliation.py	83.51% <0.00%> (ø)
erpnext/utilities/doctype/video/video.py	22.22% <0.00%> (ø)
erpnext/controllers/stock_controller.py	92.12% <81.81%> (-0.26%)	⬇️
...xt/accounts/doctype/payment_entry/payment_entry.py	72.79% <100.00%> (ø)
...ounts/doctype/purchase_invoice/purchase_invoice.py	83.83% <100.00%> (+0.07%)	⬆️
erpnext/controllers/selling_controller.py	79.56% <100.00%> (ø)
erpnext/stock/doctype/item/item.py	85.45% <100.00%> (ø)
erpnext/stock/stock_ledger.py	90.27% <100.00%> (+0.10%)	⬆️
...unts/report/purchase_register/purchase_register.py	34.21% <0.00%> (-37.51%)	⬇️
... and 46 more