Summary:
- Also converted sandboxUtil to typescript.
- The issue with %s manifested when a Python traceback contained "%s" in the
string; in that case the object with log metadata (e.g. docId) would
confusingly replace %s as if it were part of the message from Python.
Test Plan: Added a test case for the fix.
Reviewers: alexmojaki
Reviewed By: alexmojaki
Differential Revision: https://phab.getgrist.com/D3486
