[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 68.48%. Comparing base (253a51a) to head (57fc6e2).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #640      +/-   ##
============================================
+ Coverage     68.39%   68.48%   +0.09%     
  Complexity     1181     1181              
============================================
  Files           323      323              
  Lines         13125    13125              
  Branches       1316     1316              
============================================
+ Hits           8977     8989      +12     
+ Misses         3595     3586       -9     
+ Partials        553      550       -3     

Flag	Coverage Δ
hardhat	98.52% <ø> (-0.43%)	⬇️
kotlin	66.14% <ø> (+0.13%)	⬆️

see 4 files with indirect coverage changes