Refactor Partitioner to use ChunkedNodeGroupCollection

[ray6080]

• move ChunkedNodeGroupCollection to separate files with a bit more append/merge interfaces.
• refactor Partitioner to use ChunkedNodeGroupCollection.

[codecov]

Codecov Report

Attention: Patch coverage is 98.94737% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 91.91%. Comparing base (f9bc0c6) to head (0a10f6f).

Files	Patch %	Lines
...rc/processor/operator/persistent/index_builder.cpp	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3123      +/-   ##
==========================================
+ Coverage   91.89%   91.91%   +0.02%     
==========================================
  Files        1169     1171       +2     
  Lines       43774    43791      +17     
==========================================
+ Hits        40227    40252      +25     
+ Misses       3547     3539       -8     

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