Added RC-CR^2 filter

[SamuelBorden]

I've added a recursive RC-CR^2 filter that is generically useful, but has specific use cases for identifying and tagging pile-up events. I've also added a function called bi_level_zero_crossing_time_points that returns the idx of a 0 crossing in-between crossings of both a positive and negative threshold within a gate time. This function is useful for identifying the number and polarity of pileup events within an RC-CR^2 filtered waveform.

[codecov]

Codecov Report

Attention: Patch coverage is 45.00000% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 61.45%. Comparing base (74dfe76) to head (a7d18d3).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/dspeed/processors/time_point_thresh.py	4.54%	42 Missing ⚠️
src/dspeed/processors/rc_cr2.py	94.28%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
- Coverage   61.87%   61.45%   -0.43%     
==========================================
  Files          46       47       +1     
  Lines        3111     3191      +80     
==========================================
+ Hits         1925     1961      +36     
- Misses       1186     1230      +44     

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[iguinn]

I'm a little confused as to why the code coverage bot is claiming such low test coverage for the bi-level zero crossing filter given that you wrote a test...My best guess is that it's related to this issue #61 since it has two (m) output dimensions. In any case, I'll accept this and revisit when someone is able to work on that problem.