Fix control_filters tests

[christophfroehlich]

The problem of #234 was that the executor in the separate thread sometimes just doesn't stop spinning, and the join() method hangs. But with these tests, we don't need a spinning node (we just use the parameter and logging interface).

To simplify things, I moved that to a common test_fixture.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.70%. Comparing base (f0d4400) to head (7692600).
Report is 1 commits behind head on ros2-master.

Additional details and impacted files

@@               Coverage Diff               @@
##           ros2-master     #261      +/-   ##
===============================================
- Coverage        75.15%   74.70%   -0.46%     
===============================================
  Files               26       24       -2     
  Lines             1131     1099      -32     
  Branches            89       86       -3     
===============================================
- Hits               850      821      -29     
  Misses             231      231              
+ Partials            50       47       -3     

Flag	Coverage Δ
unittests	74.70% <100.00%> (-0.46%)	⬇️

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Files with missing lines	Coverage Δ
test/control_filters/test_exponential_filter.cpp	100.00% <100.00%> (ø)
test/control_filters/test_filter_util.hpp	100.00% <100.00%> (ø)
test/control_filters/test_low_pass_filter.cpp	100.00% <100.00%> (ø)
test/control_filters/test_rate_limiter.cpp	100.00% <100.00%> (ø)