API: Use integer and uint64 to better express the genesis schema

[jannotti]

This will allow generator to understand create model types.

Summary

Test Plan

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.61%. Comparing base (8341e41) to head (986752f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6311   +/-   ##
=======================================
  Coverage   51.60%   51.61%           
=======================================
  Files         649      649           
  Lines       87048    87048           
=======================================
+ Hits        44923    44929    +6     
+ Misses      39263    39256    -7     
- Partials     2862     2863    +1     

☔ 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.