Add GPSBroadcaster

[Wiktor-99]

As in the title. I'm open to any suggestions.

[codecov]

Codecov Report

Attention: Patch coverage is 86.09272% with 21 lines in your changes missing coverage. Please review.

Project coverage is 84.28%. Comparing base (28845e6) to head (d21ae07).
Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
..._sensor_broadcaster/src/gps_sensor_broadcaster.cpp	71.23%	21 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1554      +/-   ##
==========================================
+ Coverage   84.26%   84.28%   +0.02%     
==========================================
  Files         123      126       +3     
  Lines       11358    11508     +150     
  Branches      961      962       +1     
==========================================
+ Hits         9571     9700     +129     
- Misses       1471     1492      +21     
  Partials      316      316              

Flag	Coverage Δ
unittests	84.28% <86.09%> (+0.02%)	⬆️

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

Files with missing lines	Coverage Δ
...r_broadcaster/test/test_gps_sensor_broadcaster.cpp	100.00% <100.00%> (ø)
...adcaster/test/test_load_gps_sensor_broadcaster.cpp	100.00% <100.00%> (ø)
..._sensor_broadcaster/src/gps_sensor_broadcaster.cpp	71.23% <71.23%> (ø)

... and 4 files with indirect coverage changes

[saikishor]

Thank you for this new controller. I've found some on quick look
I'll send more reviews during this week.

[Timple]

Conceptual question:

We also have battery_state_broadcaster. Now we get a gps_broadcaster.

Now I can imagine we get a lot of future PR's creating packages for all items in this list: sensor_msgs.

Would it make sense to template this such that we can simply send any message from sensor_msgs?

[Wiktor-99]

@Timple Perhaps you're right; it could be a template class. However, since all sensors would use a different set of state interfaces, we would probably need to create a bunch of new semantic components (which can be done).

Also, it looks like this decision was already settled. We've got pose/IMU/range broadcasters, and templating them would affect existing configs.