[RTPublisher] use NON_POLLING as default for the realtime pubisher

[saikishor]

Fixes: #212

As reported by @bijoua29

I ran some tests with non-polling in some controllers and perf doesn't even report the sleep anymore. Most of the work is now in the DDS publish() method.

I did another test where I compiled realtime_tools from source and set it to non-polling. When I ran my full stack, the CPU usage of ros2 control node reduced from ~75% to ~52% CPU i.e. around a 30% reduction in CPU usage. Note: this is percent of 1 CPU so since I have 32 CPUs the actual usage is 1/32 of that.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.76%. Comparing base (c9639fb) to head (711b973).

Files with missing lines	Patch %	Lines
include/realtime_tools/realtime_publisher.hpp	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #280      +/-   ##
==========================================
- Coverage   72.25%   71.76%   -0.50%     
==========================================
  Files           8        8              
  Lines         483      471      -12     
  Branches       77       74       -3     
==========================================
- Hits          349      338      -11     
+ Misses         87       86       -1     
  Partials       47       47              

Flag	Coverage Δ
unittests	71.76% <87.50%> (-0.50%)	⬇️

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

Files with missing lines	Coverage Δ
include/realtime_tools/realtime_publisher.hpp	97.67% <87.50%> (+1.31%)	⬆️

[christophfroehlich]

Thanks for the cleanup and even improving it. LGTM, but let's wait for some real-world tests

[destogl]

Great work! Thanks!