[Feat] Remove flattened contracts

[kyzooghost]

This PR implements issue(s) #632

Changelog

• Removed flattened contracts with fixed pragmas
• Removed contract upgrade tests using above flattened contracts, replace with placeholder comments
• Add artifacts representing production deployments
• Add versions to TokenBridge and L2MessageService build artifacts and deploy scripts

Checklist

• I wrote new tests for my new core changes.
• I have successfully ran tests, style checker and build against my new changes locally.
• I have informed the team of any breaking changes if there are any.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.37%. Comparing base (1a811f4) to head (fe3f6bd).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #640      +/-   ##
============================================
- Coverage     68.39%   68.37%   -0.03%     
- Complexity     1181     1182       +1     
============================================
  Files           323      323              
  Lines         13125    13125              
  Branches       1316     1316              
============================================
- Hits           8977     8974       -3     
- Misses         3595     3598       +3     
  Partials        553      553              

Flag	Coverage Δ
hardhat	98.52% <ø> (-0.43%)	⬇️
kotlin	66.02% <ø> (+<0.01%)	⬆️

see 2 files with indirect coverage changes