Remove GZ_PHYSICS_ENGINE_INSTALL_DIR deprecation warnings

[caguero]

This patch removes three warnings:

/home/caguero/harmonic_ws/src/gz-sim/src/systems/physics/Physics.cc:809:13: warning: 'GZ_PHYSICS_ENGINE_INSTALL_DIR' macro is deprecated, use gz::physics::getEngineInstallDir() function instead. 
  809 |   systemPaths.AddPluginPaths({GZ_PHYSICS_ENGINE_INSTALL_DIR});
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                              
/home/caguero/harmonic_ws/src/gz-sim/src/systems/physics/EntityFeatureMap_TEST.cc:60:13: warning: 'GZ_PHYSICS_ENGINE_INSTALL_DIR' macro is deprecated, use gz::physics::getEngineInstallDir() function instead. 
   60 |     systemPaths.AddPluginPaths({GZ_PHYSICS_ENGINE_INSTALL_DIR});
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                            
/home/caguero/harmonic_ws/src/gz-sim/test/integration/tracked_vehicle_system.cc:114:13: warning: 'GZ_PHYSICS_ENGINE_INSTALL_DIR' macro is deprecated, use gz::physics::getEngineInstallDir() function instead. 
  114 |     systemPaths.AddPluginPaths({GZ_PHYSICS_ENGINE_INSTALL_DIR});
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                            
---

Summary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[azeey]

macOS is failing to build

make[2]: *** [src/systems/physics/CMakeFiles/UNIT_EntityFeatureMap_TEST.dir/EntityFeatureMap_TEST.cc.o] Error 1
make[1]: *** [src/systems/physics/CMakeFiles/UNIT_EntityFeatureMap_TEST.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 68%] Built target INTEGRATION_examples_build
[ 68%] Building CXX object test/integration/CMakeFiles/INTEGRATION_hydrodynamics.dir/hydrodynamics.cc.o
[ 68%] Linking CXX executable ../../bin/INTEGRATION_halt_motion
[ 68%] Built target INTEGRATION_follow_actor_system
[ 68%] Linking CXX executable ../../bin/INTEGRATION_hydrodynamics
[ 68%] Built target INTEGRATION_force_torque_system
[ 68%] Built target INTEGRATION_fuel_cached_server
[ 68%] Built target INTEGRATION_halt_motion
[ 68%] Built target INTEGRATION_hydrodynamics
/Users/jenkins/jenkins-agent/workspace/ignition_gazebo-ci-pr_any-homebrew-amd64/ign-gazebo/src/systems/physics/Physics.cc:51:10: fatal error: 'gz/physics/InstallationDirectories.hh' file not found
#include <gz/physics/InstallationDirectories.hh>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make[2]: *** [src/systems/physics/CMakeFiles/gz-sim8-physics-system.dir/Physics.cc.o] Error 1
make[1]: *** [src/systems/physics/CMakeFiles/gz-sim8-physics-system.dir/all] Error 2

[scpeters]

we need another prerelease of gz-physics7

gazebosim/gz-physics@gz-physics7_7.0.0-pre1...gz-physics7

[codecov]

Codecov Report

Merging #2106 (f12d5d9) into gz-sim8 (8e7f612) will increase coverage by 0.12%.
Report is 1 commits behind head on gz-sim8.
The diff coverage is 91.94%.

❗ Current head f12d5d9 differs from pull request most recent head 886daba. Consider uploading reports for the commit 886daba to get more accurate results

@@             Coverage Diff             @@
##           gz-sim8    #2106      +/-   ##
===========================================
+ Coverage    65.34%   65.47%   +0.12%     
===========================================
  Files          322      323       +1     
  Lines        30554    30699     +145     
===========================================
+ Hits         19967    20100     +133     
- Misses       10587    10599      +12     

Files Changed	Coverage Δ
src/Server.cc	87.07% <80.00%> (-0.06%)	⬇️
src/MeshInertiaCalculator.cc	92.75% <92.75%> (ø)
src/systems/physics/Physics.cc	71.90% <100.00%> (-0.07%)	⬇️

[iche033]

@osrf-jenkins run tests please

[iche033]

homebrew build fixed