Update trailing commas rule to apply to all comma-separated lists

[calda]

Summary

This PR updates the trailing commas rule to apply to all comma-separated lists, including function calls and function declarations.

let terrestrialPlanets = [
  mercury,
  venus,
  earth,
  mars,
]

func buildSolarSystem(
  innerPlanets: [Planet],
  outerPlanets: [Planet],
) { ... }

buildSolarSystem(
  innertPlanets: terrestrialPlanets,
  outerPlanets: gasGiants,
)

This PR also refines the rule to omit the trailing comma if the list only contains a single element. We feel this is especially the right choice in function calls with only a single argument, where the trailing commas adds unnecessary noise:

// WRONG
let planetsWithLife = [
  earth,
]

func buildSolarSystem(
  _ planets: [Planet],
)

buildSolarSystem(
  terrestrialPlanets + gasGiants,
)

// RIGHT
let planetsWithLife = [
  earth
]

func buildSolarSystem(
  _ planets: [Planet]
) { ... }

buildSolarSystem(
  terrestrialPlanets + gasGiants
)