Add fix costs on bialteralized gas pipe trade

[junukitashepard]

This PR ensures that by default, fixed costs are added to the piped gas trade technology.

Fixed costs in the bilateralize tool represent existing trade proclivities, and exist primarily to differentiate among different trade relations. For example, if WEU>MEA fix_cost is 100 and WEU>CHN fix_cost is 50 for the same commodity (e.g., piped gas) then this will be part of the "decision" for whether and how much WEU/MEA and WEU/CHN trade with one another. This is in combination with distance and other infrastructural costs (e.g., costs associated with building and operating the pipelines)

How to review

Required: describe specific things that reviewer(s) must do, in order to ensure that the PR achieves its goal.
If no review is required, write “No review:” and describe why.

PR checklist

• Continuous integration checks all ✅
• Update doc/whatsnew.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.5%. Comparing base (54fe267) to head (2512cc9).

Files with missing lines	Patch %	Lines
...odels/tools/bilateralize/historical_calibration.py	0.0%	6 Missing ⚠️
...ssage_ix_models/tools/bilateralize/prepare_edit.py	0.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #478     +/-   ##
=======================================
- Coverage   69.5%   69.5%   -0.1%     
=======================================
  Files        300     300             
  Lines      24598   24603      +5     
=======================================
- Hits       17104   17103      -1     
- Misses      7494    7500      +6     

Files with missing lines	Coverage Δ
...ssage_ix_models/tools/bilateralize/prepare_edit.py	89.7% <0.0%> (ø)
...odels/tools/bilateralize/historical_calibration.py	26.2% <0.0%> (-0.5%)	⬇️

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.