[ENHANCEMENT] Update run_dynamics_fast to abide by naming rules

### Relation

The MATLAB mex function, [`run_dynamics_fast`](https://github.com/Airspace-Encounter-Models/em-core/blob/master/matlab/utilities-1stparty/runDynamicsFast/run_dynamics_fast.c) is used by multiple repositories, including `em-model-manned-bayes` to simulate aircraft trajectories with a 6DOF physics model. The code does not abide by consistent naming rules.

### Description

Update the code to abide by the Google C++ Style Guide [naming rules](https://google.github.io/styleguide/cppguide.html#Naming)

### Alternatives

There are various style guides, if the assignee or contributor recommends a different style please comment on the issue and explain why.

### Additional

Recommend addressing issue #10 for the use `const` variables before addressing this issue, as `const` variables have a different naming convention.

While the contributing guidelines does not define a style guide for C++, we currently recommend the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) for this issue.