refactor: disallow bank transactions on different currencies

[ruthra-kumar]

Prevent Bank Transaction's on a different currency to the Bank Account currency.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (e53931e) 60.04% compared to head (a27a4db) 60.07%.
Report is 71 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #39336      +/-   ##
===========================================
+ Coverage    60.04%   60.07%   +0.03%     
===========================================
  Files          761      757       -4     
  Lines        70459    70418      -41     
===========================================
- Hits         42304    42303       -1     
+ Misses       28155    28115      -40     

Files	Coverage Δ
...cturing/doctype/production_plan/production_plan.py	80.70% <100.00%> (-0.13%)	⬇️
...ounts/doctype/bank_transaction/bank_transaction.py	63.30% <87.50%> (+3.20%)	⬆️
erpnext/controllers/accounts_controller.py	85.11% <50.00%> (+0.01%)	⬆️

... and 18 files with indirect coverage changes