Enable negative starts and ends for slice op

[johnhuichen]

Pull Request Template

Checklist

• Confirmed that run-checks all script has been executed.
• Made sure the book is up to date with changes in this PR.

Related Issues/PRs

#1714

Changes

Per https://onnx.ai/onnx/operators/onnx__Slice.html, slice's input parameters starts and ends accept negative parameters.

When start or end is negative, it is made positive by adding the corresponding tensor dim to it.

Testing

# update onnx
python /path/to/slice.py

cargo xtask run-checks all

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.51%. Comparing base (d6efb3c) to head (8442d13).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1981      +/-   ##
==========================================
- Coverage   85.64%   85.51%   -0.14%     
==========================================
  Files         810      811       +1     
  Lines      100145   100413     +268     
==========================================
+ Hits        85768    85864      +96     
- Misses      14377    14549     +172     

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[antimora]

LGTM. Thanks for fixing it!