ci(build): bump solidity version to v0.8.23 and parallelize tests

[milapsheth]

• [x] Bump Solidity to v0.8.23
• [x] Fix contracts that aren't changing
• [x] Only run tests against London EVM version, i.e restrict official support to London
• [x] Run tests for gh actions in parallel mode

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.00%. Comparing base (58e74c3) to head (17f4dd1).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #147 +/- ## ======================================= Coverage 96.00% 96.00% ======================================= Files 47 47 Lines 725 725 Branches 157 157 ======================================= Hits 696 696 Misses 6 6 Partials 23 23 ```

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