fix: erase UOMs when changing stock UOM

[anupamvs]

Issue- When item's default stock UOM is changed, the old conversion factors become unusable, erase UOM conversion list upon updating stock UOM.

[codecov]

Codecov Report

Merging #29062 (50f9a4d) into develop (5cda4ea) will decrease coverage by 0.30%.
The diff coverage is 100.00%.

❗ Current head 50f9a4d differs from pull request most recent head d3806db. Consider uploading reports for the commit d3806db to get more accurate results

@@             Coverage Diff             @@
##           develop   #29062      +/-   ##
===========================================
- Coverage    58.06%   57.75%   -0.31%     
===========================================
  Files         1110     1107       -3     
  Lines        68007    67912      -95     
===========================================
- Hits         39489    39225     -264     
- Misses       28518    28687     +169     

Impacted Files	Coverage Δ
erpnext/stock/doctype/item/item.py	66.88% <100.00%> (+0.08%)	⬆️
...work_order_stock_report/work_order_stock_report.py	50.00% <0.00%> (-50.00%)	⬇️
...unts/report/purchase_register/purchase_register.py	34.24% <0.00%> (-45.90%)	⬇️
...ext/accounts/report/balance_sheet/balance_sheet.py	36.36% <0.00%> (-21.82%)	⬇️
...e_purchase_register/item_wise_purchase_register.py	58.00% <0.00%> (-20.00%)	⬇️
...em_wise_sales_register/item_wise_sales_register.py	51.36% <0.00%> (-12.28%)	⬇️
...t/accounts/report/sales_register/sales_register.py	73.33% <0.00%> (-7.28%)	⬇️
...next/accounts/doctype/pricing_rule/pricing_rule.py	65.59% <0.00%> (-5.74%)	⬇️
.../manufacturing/report/bom_explorer/bom_explorer.py	94.44% <0.00%> (-5.56%)	⬇️
erpnext/setup/utils.py	84.26% <0.00%> (-5.43%)	⬇️
... and 40 more

[anupamvs]

@Mergifyio backport version-13-hotfix

[ankush]

1. mutating list while iterating over it will lead to runtime errors.
2. it's simpler to just reset the index instead of this complicated logic. Once all modifications are done...

for idx, row in enumerate(doc.child_table, start=1):
    row.idx = idx

[ankush]

just realized something very basic.

When stock UOM change, the old conversions don't make sense at all. They all need to be removed 😄

e.g.

• Nos is default stock UOM
• 20 Nos = 1 Box
• You change default stock UOM to Kg and now conversion is 20 Nos = 1KG now.

IMO lets just erase the whole table and show toast that UOM conversions are cleared.