refactor: update_serial_no function for old Maintenance Visits

[noahjacob]

Issue

• Old documents which were saved before the refactor would not have the "Maintenance Schedule Detail" field set.

Fix

• Using maintenance_schedule field in "Maintenance Visit" to fetch the serial nos instead of the Maintenance Schedule Detail row id, which isn't possible to identify on old docs.
• Patch to update this field on old docs that have prevdoc_docname.

To Test:

• Make an independent maintenance visit (not from maintenance schedule) and see if it works fine. Use serialised item in it and add serial nos > Add multiple serialised items and see if you can select appropriate serial nos (check the filters)
• Make a maintenance schedule with multiple items, 1 non serialised, 2 serialised. Make visits, see if it works and updates the schedule correctly

[codecov]

Codecov Report

Merging #28843 (dec7513) into develop (9088984) will increase coverage by 0.08%.
The diff coverage is 90.00%.

@@             Coverage Diff             @@
##           develop   #28843      +/-   ##
===========================================
+ Coverage    57.96%   58.05%   +0.08%     
===========================================
  Files         1110     1110              
  Lines        68080    68088       +8     
===========================================
+ Hits         39464    39528      +64     
+ Misses       28616    28560      -56     

Impacted Files	Coverage Δ
...nce/doctype/maintenance_visit/maintenance_visit.py	51.25% <75.00%> (+1.25%)	⬆️
...ctype/maintenance_schedule/maintenance_schedule.py	85.83% <100.00%> (+9.24%)	⬆️
...t/accounts/report/sales_register/sales_register.py	73.33% <0.00%> (-5.46%)	⬇️
...em_wise_sales_register/item_wise_sales_register.py	61.36% <0.00%> (-1.82%)	⬇️
erpnext/hr/doctype/attendance/attendance.py	40.54% <0.00%> (-1.52%)	⬇️
erpnext/crm/doctype/prospect/prospect.py	55.22% <0.00%> (-1.50%)	⬇️
erpnext/stock/report/stock_ledger/stock_ledger.py	77.23% <0.00%> (-0.82%)	⬇️
erpnext/selling/doctype/quotation/quotation.py	49.18% <0.00%> (-0.55%)	⬇️
erpnext/selling/doctype/sales_order/sales_order.py	77.29% <0.00%> (-0.39%)	⬇️
...stock/doctype/purchase_receipt/purchase_receipt.py	90.42% <0.00%> (-0.27%)	⬇️
... and 21 more

[marination]

@Mergifyio backport version-13-hotfix

[mergify]

backport version-13-hotfix

✅ Backports have been created

• #29352 refactor: update_serial_no function for old Maintenance Visits (backport #28843) has been created for branch version-13-hotfix