only use chr(30) and chr(31) delimiters

[splch]

• update tests to remove\u* and \x*

relates to #5216

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.37%. Comparing base (704913b) to head (6198e8d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7699      +/-   ##
==========================================
- Coverage   99.38%   99.37%   -0.01%     
==========================================
  Files        1089     1089              
  Lines       97550    97551       +1     
==========================================
- Hits        96948    96946       -2     
- Misses        602      605       +3     

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[mhucka]

@splch Thank you for your work on this! When you get a chance, could you update the title of this PR to mention that this is for cirq-ionq, and also add a bit more explanation to the PR description? This will help future contributors and maintainers when reading and searching through past work.