Allow findfirst(isone) and findfirst(iszero) for InfRanges

[DanielVandH]

Fixes #178

Also changes my previous PR #177 to use the new findfirst(iszero)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.14%. Comparing base (d6eaad4) to head (c4c2b74).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
- Coverage   86.00%   85.14%   -0.86%     
==========================================
  Files           6        6              
  Lines         743      754      +11     
==========================================
+ Hits          639      642       +3     
- Misses        104      112       +8     

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[DanielVandH]

This doesn't work for reversed ranges..

findfirst(==(1), 10:-1:-∞) # should be 10?

Should it? Probably it's own issue since this issue already exists on master #180