fix: incorrect serial no valuation

[ankush]

Steps to reproduce:

1. have multiple serial nos with different rates
2. Create a delivery for 1 serial no; do not submit.
3. Update serial number to some other number with different purchase/manufacture rates.
4. Submit and check stock value difference. It should be same as incoming rate but it would be from previous serial no instead.

caused by & potentially affected use cases: #25306 & #27036

To Test:

• The case above
• Delivery return of a serial no (single) and multiple serial nos

[codecov]

Codecov Report

Merging #28987 (5d27a76) into develop (3438e1f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop   #28987   +/-   ##
========================================
  Coverage    57.93%   57.93%           
========================================
  Files         1110     1110           
  Lines        68087    68087           
========================================
  Hits         39449    39449           
  Misses       28638    28638           

Impacted Files	Coverage Δ
erpnext/controllers/selling_controller.py	79.06% <100.00%> (ø)
erpnext/stock/stock_ledger.py	85.76% <100.00%> (+0.36%)	⬆️
...eport/item_variant_details/item_variant_details.py	31.32% <0.00%> (-56.63%)	⬇️
...wise_balance_history/batch_wise_balance_history.py	68.96% <0.00%> (-24.14%)	⬇️
...xt/stock/report/stock_analytics/stock_analytics.py	91.08% <0.00%> (-1.99%)	⬇️
...eorder_level/itemwise_recommended_reorder_level.py	92.45% <0.00%> (-1.89%)	⬇️
erpnext/stock/reorder_item.py	76.06% <0.00%> (-1.71%)	⬇️
...r/doctype/leave_ledger_entry/leave_ledger_entry.py	90.16% <0.00%> (-1.64%)	⬇️
erpnext/stock/report/stock_ledger/stock_ledger.py	76.42% <0.00%> (-1.63%)	⬇️
.../report/stock_projected_qty/stock_projected_qty.py	88.15% <0.00%> (-1.32%)	⬇️
... and 26 more