chore: update Node.js to v20 and implement Promise.all optimization

[phessophissy]

Summary

Modernize the codebase with Node.js updates and performance improvements.

Changes

• Update Node.js from v16 to v20 - Node 16 reached End-of-Life in September 2023
  • Updated maker.Dockerfile (both builder and production stages)
  • Updated serverless.yml runtime to nodejs20.x
• Implement Promise.all() optimization in makerRoutine()
  • Resolves the TODO comment in the code
  • Markets are now processed in parallel instead of sequentially
  • Gas price check moved outside the loop for efficiency

Testing

• Code compiles successfully
• Logic remains the same, just parallelized for better performance