Fix build with Apple Clang

[Yadunund]

Depends on open-rmf/rmf_utils#27

When building on macOS with the default Apple Compiler, several build errors are thrown as seen below (small sample)

  virtual std::shared_ptr<const ParticipantDescription> get_participant(
                                                        ^
/Users/yadunund/ws_rmf/src/rmf/rmf_traffic/rmf_traffic/include/rmf_traffic/schedule/Viewer.hpp:134:40: note: unimplemented pure virtual method 'get_itinerary' in 'Database'
  virtual std::optional<ItineraryView> get_itinerary(
                                       ^
/Users/yadunund/ws_rmf/src/rmf/rmf_traffic/rmf_traffic/include/rmf_traffic/schedule/Viewer.hpp:140:33: note: unimplemented pure virtual method 'get_current_plan_id' in 'Database'
  virtual std::optional<PlanId> get_current_plan_id(

It looks like the base classes such as Viewer or ItineraryViewer have virtual methods with ParticipantID as argument type whereas classes that implement these methods such as Database or Mirror replace ParticipantId with std::size_t. As a result the compiler think we're wrongly implementing the virtual methods.

I'm actually surprised gcc or llvm-clang doesn't catch this same error?
I'm also assuming this change will break API/ABI so perhaps this should not be backported into humble

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 23.01%. Comparing base (8274fd2) to head (177138d).

❗ Current head 177138d differs from pull request most recent head 2cd027f

Please upload reports for the commit 2cd027f to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
+ Coverage   21.71%   23.01%   +1.30%     
==========================================
  Files         361      369       +8     
  Lines       30302    30769     +467     
  Branches    14200    14371     +171     
==========================================
+ Hits         6580     7083     +503     
- Misses      14218    14235      +17     
+ Partials     9504     9451      -53     

Flag	Coverage Δ
tests	22.89% <100.00%> (+1.17%)	⬆️

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

Files	Coverage Δ
..._traffic/include/rmf_traffic/schedule/Database.hpp	0.00% <ø> (ø)
...mf_traffic/include/rmf_traffic/schedule/Mirror.hpp	0.00% <ø> (ø)
rmf_traffic/src/rmf_traffic/schedule/Database.cpp	49.23% <ø> (+1.98%)	⬆️
rmf_traffic/src/rmf_traffic/schedule/Mirror.cpp	41.79% <ø> (+1.58%)	⬆️
rmf_traffic/test/unit/schedule/test_Spacetime.cpp	38.71% <100.00%> (+8.80%)	⬆️

... and 149 files with indirect coverage changes