simplify user-facing python code + fix typos

[mikeroberts3000]

Please address outstanding comments.

[mikeroberts3000]

@RachithP

• Rename navmesh_env.py to navmesh.py to match the name of the class in the file. In my previous comment, I didn't mean that we must name all files that provide higher-level functionality as *_env.py. I just meant that we should cleanly separate standalone functions in _utils.py files, and higher-level functionality in other files.
• Move all service functionality that doesn't need to be in a header into cpp files. If something doesn't need to be in a header, it shouldn't be. We can make exceptions for extremely simple one-liner functions, if putting them in a header would make it so we don't need a cpp file at all. But the service implementations don't meet that criteria.

[RachithP]

@RachithP

• Rename navmesh_env.py to navmesh.py to match the name of the class in the file. In my previous comment, I didn't mean that we must name all files that provide higher-level functionality as *_env.py. I just meant that we should cleanly separate standalone functions in _utils.py files, and higher-level functionality in other files.

Made these changes in https://github.com/isl-org/spear/pull/279.

• Move all service functionality that doesn't need to be in a header into cpp files. If something doesn't need to be in a header, it shouldn't be. We can make exceptions for extremely simple one-liner functions, if putting them in a header would make it so we don't need a cpp file at all. But the service implementations don't meet that criteria.

Since our EngineService class is templated, we can't move it to a cpp file. However, only constructors of other service classes are templated, so we can move their member functions to a cpp file. Made these changes in https://github.com/isl-org/spear/pull/279 . Note that to maintain symmetry with the constructors, I kept the destructors in the header file.

[mikeroberts3000]

Note that to maintain symmetry with the constructors, I kept the destructors in the header file.

Great choice. It's nice to see the constructor next to the destructor, even if we could move the destructor to a cpp file.