refactor: gain/loss je should use same posting date as payment

[ruthra-kumar]

Gain/Loss JE should use the same posting date as the Payment it is referencing

[codecov]

Codecov Report

Merging #36950 (f7865da) into develop (75d95ac) will decrease coverage by 0.01%.
Report is 20 commits behind head on develop.
The diff coverage is 79.97%.

@@             Coverage Diff             @@
##           develop   #36950      +/-   ##
===========================================
- Coverage    65.55%   65.55%   -0.01%     
===========================================
  Files          796      796              
  Lines        62717    62718       +1     
===========================================
  Hits         41114    41114              
- Misses       21603    21604       +1     

Files Changed	Coverage
...e/payment_reconciliation/payment_reconciliation.py	ø
erpnext/assets/doctype/asset/asset.py	0.00%
...ctype/asset_capitalization/asset_capitalization.py	ø
...ctype/stock_reconciliation/stock_reconciliation.py	ø
...rpnext/stock/report/stock_balance/stock_balance.py	ø
...next/stock/report/reserved_stock/reserved_stock.py	46.66%
erpnext/controllers/accounts_controller.py	50.00%
...ext/stock/doctype/stock_settings/stock_settings.py	50.00%
erpnext/stock/doctype/pick_list/pick_list.py	56.86%
erpnext/stock/stock_ledger.py	66.66%
... and 15 more