Add standalone version of LPF

[christophfroehlich]

Replaces #192 and closes #164

Changes on top:

• I changed the base class to be independent of filters
• Used the old class/file name and moved the new one to control_toolbox namespace.

The filter plugins should still work as before without any changes (see the test files).

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 70.78652% with 26 lines in your changes missing coverage. Please review.

Project coverage is 51.17%. Comparing base (e05102c) to head (b85a21d).
Report is 1 commits behind head on ros2-master.

Files with missing lines	Patch %	Lines
include/control_filters/low_pass_filter_ros.hpp	60.00%	12 Missing and 4 partials ⚠️
include/control_toolbox/low_pass_filter.hpp	79.59%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           ros2-master     #222      +/-   ##
===============================================
+ Coverage        50.41%   51.17%   +0.76%     
===============================================
  Files                9       10       +1     
  Lines              486      510      +24     
  Branches            62       66       +4     
===============================================
+ Hits               245      261      +16     
- Misses             215      221       +6     
- Partials            26       28       +2     

Flag	Coverage Δ
unittests	51.17% <70.78%> (+0.76%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
include/control_toolbox/low_pass_filter.hpp	79.59% <79.59%> (ø)
include/control_filters/low_pass_filter_ros.hpp	60.00% <60.00%> (ø)

[christophfroehlich]

@roncapat what do you think?

[roncapat]

@roncapat what do you think?

Nice for me! Thank you 👍🏻