Use tsdownsample library for downsampling if available

[philippjfr]

Partially resolves -> #6058

[codecov-commenter]

Codecov Report

Attention: 19 lines in your changes are missing coverage. Please review.

Comparison is base (307b1fb) 88.66% compared to head (0e2316c) 88.64%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
holoviews/operation/downsample.py	45.71%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6059      +/-   ##
==========================================
- Coverage   88.66%   88.64%   -0.03%     
==========================================
  Files         314      314              
  Lines       65764    65794      +30     
==========================================
+ Hits        58309    58321      +12     
- Misses       7455     7473      +18     

Flag	Coverage Δ
ui-tests	23.65% <22.85%> (-0.01%)	⬇️

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