test: remove unnecessary creation of companies

[ankush]

Tests end up creating 19-20 companies... some for really bad uses 🤦

For instance in one test, to check abbreviations are correctly concatenated a whole new company is getting created 🥲

• removed "New from Existing Company For Test"
• changed the country for others to ones with no fixtures.
• remove new country creation for shipment test.

Results: this test run is actually slower (LOL) due to randomness. But you can kinda expect 30-40 seconds saving per run.

[codecov]

Codecov Report

Merging #28965 (e31ed37) into develop (66a10c0) will decrease coverage by 0.00%.
The diff coverage is 50.00%.

@@             Coverage Diff             @@
##           develop   #28965      +/-   ##
===========================================
- Coverage    55.59%   55.58%   -0.01%     
===========================================
  Files         1128     1128              
  Lines        67285    67287       +2     
===========================================
- Hits         37404    37400       -4     
- Misses       29881    29887       +6     

Impacted Files	Coverage Δ
erpnext/__init__.py	69.87% <50.00%> (ø)
...work_order_stock_report/work_order_stock_report.py	50.00% <0.00%> (-44.12%)	⬇️
...wise_balance_history/batch_wise_balance_history.py	68.96% <0.00%> (-24.14%)	⬇️
.../manufacturing/report/bom_explorer/bom_explorer.py	94.44% <0.00%> (-5.56%)	⬇️
...eport/item_variant_details/item_variant_details.py	84.33% <0.00%> (-3.62%)	⬇️
.../report/stock_projected_qty/stock_projected_qty.py	86.84% <0.00%> (-2.64%)	⬇️
...ctype/accounting_dimension/accounting_dimension.py	64.06% <0.00%> (-1.57%)	⬇️
.../hr/doctype/upload_attendance/upload_attendance.py	44.69% <0.00%> (-1.52%)	⬇️
...e/period_closing_voucher/period_closing_voucher.py	88.23% <0.00%> (-1.48%)	⬇️
erpnext/portal/utils.py	28.98% <0.00%> (-1.45%)	⬇️
... and 20 more