speed up aggregate

[Intron7]

Template aggregate to be more composable and safe memory

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.66667% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.91%. Comparing base (8f8cc48) to head (ee1601a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rapids_singlecell/get/_aggregated.py	94.36%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #685      +/-   ##
==========================================
+ Coverage   88.88%   88.91%   +0.03%     
==========================================
  Files         103      103              
  Lines        8421     8464      +43     
==========================================
+ Hits         7485     7526      +41     
- Misses        936      938       +2     

Files with missing lines	Coverage Δ
...apids_singlecell/tools/_rank_genes_groups/_core.py	91.73% <100.00%> (+0.10%)	⬆️
src/rapids_singlecell/get/_aggregated.py	91.47% <94.36%> (+0.76%)	⬆️