MAINT: misc post-release improvements

[lizgehret]

Individual plot changes/updates

Scatterplot

• simplifies scatterplot's xy scales
• updates marks to include black outline unless hovered on
• add color palette drop-down

Lineplot

• updates lineplot's y_measure as an optional input
  • add testing to support edge cases associated with this change
• updates scatter marks to include black outline unless hovered on
• add color palette drop-down

Heatmap

• updates heatmap's xy scales to call width/height directly

Boxplot

• add color palette drop-down

---

Standardizations/misc housekeeping

• standardizes vega spec order/formatting across all visualizers
• adds padding between title/subtitle & main plot for all visualizers
• removes community CI workflows (no longer needed for testing purposes)