text: Title: [core] Guard ray C++ code quality via unit test
  Body: ### Description
  
  Ray core C++ components are not properly unit tested:
  - As people left, it's less confident to guard against improper code change with missing context;
  - Sanitizer on CI is only triggered on unit test;
  - Unit test coverage is a good indicator of code quality (i.e. 85% branch coverage).
  
  ### Use case
  
  _No response_