LaTeX and more simplification

This devlog was supposed to be two separate ones, but Stardance was refusing to calculate logged hours :(

There’s a big list of changes here:

• Added a label to show kinetic and potential energies (and demonstrating conservation of energy!)
• Finally implemented combining like terms (3x + 2x = 5x) and like powers (sin(x) * sin(x) = sin^2(x)), which provides a huge speed increase since the equations of motion are now simpler
• Fixed a BUNCH of bugs that were cropping up under MicroPython (annoyingly CPython’s dict keys in order of assignment is an implementation detail that isn’t in MicroPython, and the hashing function in MicroPython is completely unreliable)
• Added LaTeX mode for converting expressions into strings, which automatically handles subscripts and symbols
• Added labels to the diagram also with LaTeX, tweaked for visibility