fix: Recalculate advance_paid in SO/PO after unlinking from advance entry

[marination]

Issue:

• Create a Sales Order for Rs.100
• Create an Advance Payment Entry against the Sales Order for Rs.40
• Now advance_paid in SO = 40
• Create a final Sales Invoice against this Sales Order. Fetch advance payments and submit. Outstanding = 100 - 40 = Rs.60

Now the PE is not linked to the Sales Order anymore but to the Sales Invoice. Yet, the advance_paid in the Sales Order shows as Rs.40, it isn't recalculated.

Issues are faced when we want to cancel the advance PE (case: some data in the Sales Invoice was wrong, we had to create a credit note for the customer and cancel the Payment Entry to issue new documents).

On trying to create a new advance PE it shows allocated amount as total - advance (wrong) = 100 - 40 = 60

Fix:

Recalculate the SO/PO advance while it is being unlinked/replaced by an invoice in the PE reference

ToDo:

• Unit Test

[codecov]

Codecov Report

Merging #37069 (426350e) into develop (1c78a5a) will increase coverage by 0.00%.
Report is 9 commits behind head on develop.
The diff coverage is 75.00%.

❗ Current head 426350e differs from pull request most recent head 8a4954d. Consider uploading reports for the commit 8a4954d to get more accurate results

@@           Coverage Diff            @@
##           develop   #37069   +/-   ##
========================================
  Coverage    66.03%   66.03%           
========================================
  Files          796      796           
  Lines        62761    62765    +4     
========================================
+ Hits         41442    41448    +6     
+ Misses       21319    21317    -2     

Files Changed	Coverage
erpnext/accounts/utils.py	75.00%

[marination]

Unrelated job card test failing