[DOCS] Add grouping and aggregation docs

[colin-ho]

No description provided.

[codspeed-hq]

CodSpeed Performance Report

Merging #2805 will degrade performances by 55.01%

_{Comparing colin/agg-docs (6e07974) with main (b61349b)}

Summary

❌ 1 regressions
✅ 15 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	colin/agg-docs	Change
❌	test_show[100 Small Files]	50.6 ms	112.5 ms	-55.01%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (main@b61349b). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2805   +/-   ##
=======================================
  Coverage        ?   63.28%           
=======================================
  Files           ?     1007           
  Lines           ?   114178           
  Branches        ?        0           
=======================================
  Hits            ?    72253           
  Misses          ?    41925           
  Partials        ?        0