No functional changes
In preparation to tackle the following 2 Todos
* TODO: view scale should factor into this someday too...
* TODO: optimize this to not have to calc stuff out of view too?
I did the following cleanup
* extracted drawing code for `BEZT_IPO_BEZ` into a separate function
* extracted code that calculates the resolution between 2 points into a separate function
* cleaned up comments
* renamed variables to have a more telling name
* moved variables closer to where they are used
* added `const` where possible
Pull Request: https://projects.blender.org/blender/blender/pulls/108748
c3a2de470d