ENH: Use arrow table to transfer dataset meta

[codingl2k1]

What do these changes do?

As the issue https://github.com/xorbitsai/xorbits/issues/638 has been fixed, we can use an arrow table instead of a pandas dataframe to transfer metadata.

• [x] Optimize meta index format.
• [x] Merge chunks support arrow tables.

Related issue number

Fixes #xxxx

Check code requirements

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

[codecov[bot]]

Codecov Report

Merging #663 (694134b) into main (34f7bca) will decrease coverage by 17.09%. The diff coverage is 96.77%.

@@             Coverage Diff             @@
##             main     #663       +/-   ##
===========================================
- Coverage   93.61%   76.52%   -17.09%     
===========================================
  Files        1025     1025               
  Lines       79726    79735        +9     
  Branches    16535    16538        +3     
===========================================
- Hits        74634    61017    -13617     
- Misses       3415    16349    +12934     
- Partials     1677     2369      +692     

Flag	Coverage Δ
unittests	76.41% <96.77%> (-17.10%)	:arrow_down:

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

Files Changed	Coverage Δ
...on/xorbits/datasets/backends/huggingface/export.py	96.11% <93.33%> (-0.07%)	:arrow_down:
python/xorbits/_mars/utils.py	73.08% <100.00%> (-16.19%)	:arrow_down:
python/xorbits/datasets/iterable_dataset.py	96.79% <100.00%> (+0.09%)	:arrow_up:

... and 276 files with indirect coverage changes