Enable heightmap collision

[iche033]

🎉 New feature

Summary

Add collision to heightmap

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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.

[caguero]

Not sure if it's related with this PR but in the Entity Tree, I select Terrain->View->Collisions and get a consistent crash.

terminate called after throwing an instance of 'Ogre::RenderingAPIException'
  what():  OGRE EXCEPTION(3:RenderingAPIException): Fragment Program 700000004PixelShader_ps failed to compile. See compile log above for details. in GLSLShader::compile at ./RenderSystems/GL3Plus/src/GLSL/OgreGLSLShader.cpp (line 361)
Stack trace (most recent call last) in thread 1312635:
#10   Object "[0xffffffffffffffff]", at 0xffffffffffffffff, in 
#9    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7efe741269ff, in 
#8    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7efe74094b42, in 
#7    Object "/lib/x86_64-linux-gnu/libQt5Core.so.5", at 0x7efe6d49199d, in 
#6    Object "/lib/x86_64-linux-gnu/libQt5Core.so.5", at 0x7efe6d48ff90, in qTerminate()
#5    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7efe6f8ae276, in std::terminate()
#4    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7efe6f8ae20b, in 
#3    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x7efe6f8a2b9d, in 
#2    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7efe740287f2, in abort
#1    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7efe74042475, in raise
#0    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7efe74096a7c, in pthread_kill
Aborted (Signal sent by tkill() 1312483 1000)
[Dbg] [SignalHandler.cc:142] Received signal[2].
[Dbg] [ServerPrivate.cc:115] Server received signal[2]
[Dbg] [gz.cc:434] Shutting down gz-sim-server
[Dbg] [SimulationRunner.cc:520] Exiting postupdate worker thread (0)

[iche033]

looks like heightmap collision visualization doesn't work. I created gazebosim/gz-sim#2097 to prevent the crash