update _draw! to behave like an iterator and take a function as an argument

[Sid-Bhatia-0]

1. Update _draw! to behave like an iterator and take a function as an argument like put_pixel!, or put_pixel_undirected! or any anonymous function. This significantly increases code reuse without sacrificing performance when things are type-stable.
2. Remove inline macros for drawing Point and Background.
3. Add shapes CircleOctant and ThickCircleOctant to iterate over the first octant (i >= 0, j >=0, i >= j) for drawing these circles. Accordingly modify OddSymmetricPoints8, OddSymmetricVerticalLines4, OddSymmetricLines8, and their corresponding Even counterparts.
4. Use explicit iteration for drawing VerticalLine, HorizontalLine, and FilledRectangle.