Fix RangeSet.__len__ when defined by floats

[jsiirola]

Fixes # .

Summary/Motivation:

This resolves an error where RangeSet.__len__() raised an exception when the RangeSet was defined by float endpoints.

Changes proposed in this PR:

• Ensure that the result from RangeSet.__len__() is cast to an int
• Add a test exercising the observed error

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b41d3ae) 88.28% compared to head (714edcd) 88.29%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3119   +/-   ##
=======================================
  Coverage   88.28%   88.29%           
=======================================
  Files         832      832           
  Lines       92234    92234           
=======================================
+ Hits        81430    81438    +8     
+ Misses      10804    10796    -8     

Flag	Coverage Δ
linux	86.05% <100.00%> (+<0.01%)	⬆️
osx	75.55% <100.00%> (ø)
other	86.22% <100.00%> (ø)
win	83.45% <100.00%> (ø)

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