feat: add GroupByExec in solidity

[iajoiner]

Please be sure to look over the pull request guidelines here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/CONTRIBUTING.md#submit-pr.

Please go through the following checklist

• The PR title and commit messages adhere to guidelines here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/CONTRIBUTING.md. In particular ! is used if and only if at least one breaking change has been introduced.
• I have run the ci check script with source scripts/run_ci_checks.sh.
• I have run the clean commit check script with source scripts/check_commits.sh, and the commit history is certified to follow clean commit guidelines as described here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/COMMIT_GUIDELINES.md
• The latest changes from main have been incorporated to this PR by simple rebase if possible, if not, then conflicts are resolved appropriately.

Rationale for this change

What changes are included in this PR?

Are these changes tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.71%. Comparing base (e4be48a) to head (8cb7bec).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #774   +/-   ##
=======================================
  Coverage   96.71%   96.71%           
=======================================
  Files         332      332           
  Lines       60088    60088           
=======================================
  Hits        58114    58114           
  Misses       1974     1974           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

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