change bucket count type

[PSeitz]

closes #2012

[codecov-commenter]

Codecov Report

Merging #2013 (3d21715) into main (c599bf3) will increase coverage by 0.02%.
The diff coverage is 87.50%.

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@@            Coverage Diff             @@
##             main    #2013      +/-   ##
==========================================
+ Coverage   94.33%   94.35%   +0.02%     
==========================================
  Files         320      319       -1     
  Lines       59024    59209     +185     
==========================================
+ Hits        55678    55869     +191     
+ Misses       3346     3340       -6     

Impacted Files	Coverage Δ
src/aggregation/mod.rs	93.90% <ø> (ø)
src/aggregation/bucket/term_agg.rs	97.95% <66.66%> (ø)
src/aggregation/agg_limits.rs	100.00% <100.00%> (ø)
src/aggregation/bucket/histogram/histogram.rs	98.70% <100.00%> (ø)
src/aggregation/intermediate_agg_result.rs	94.83% <100.00%> (ø)

... and 39 files with indirect coverage changes