ggswim Redevelopment

[rsh52]

Description

This PR vastly simplifies the API for ggswim by intelligently using scales and synonymous aes techniques to handle much of what was being done with points and markers previously.

This was made possible thanks in huge part to @teunbrand and @yjunechoe and I will be sure to highlight you both for credit in this.

Proposed Changes

List changes below in bullet format:

• Remove geom_swim_point()
• Remove geom_swim_label()
• Remove {ggnewscale} dependencies, remove use of ggplot_add, remove print/build/grid methods
  • The latter can be reinstated down the line if needed
• Add geom_swim_marker()
• Add scale_marker_discrete()
• Update datasets
• Update test suite
• Update vignettes
• Update README