ENH: added auto merge for cartesian_chunk

[qinxuye]

What do these changes do?

This PR added auto merge for cartesian_chunk

Related issue number

Fixes #xxxx

Check code requirements

• tests added / passed (if needed)
• Ensure all linting tests pass

[codecov]

Codecov Report

Merging #699 (87ec47d) into main (dd999f0) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #699      +/-   ##
==========================================
- Coverage   93.50%   93.50%   -0.01%     
==========================================
  Files        1025     1025              
  Lines       79341    79353      +12     
  Branches    16442    16440       -2     
==========================================
+ Hits        74191    74197       +6     
- Misses       3463     3466       +3     
- Partials     1687     1690       +3     

Flag	Coverage Δ
unittests	93.39% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...on/xorbits/_mars/dataframe/base/cartesian_chunk.py	94.61% <100.00%> (-0.20%)	⬇️
python/xorbits/_mars/dataframe/base/core.py	100.00% <100.00%> (ø)
python/xorbits/_mars/dataframe/merge/merge.py	98.31% <100.00%> (-0.08%)	⬇️

... and 10 files with indirect coverage changes

[aresnow1]

LGTM