[Overview] Improve existing Concept Exercises

[junedev]

This is a tracking issue for the concept exercises that need some cleanup or improvement.

• Improve Concept Exercise: Numbers (Freelancer Rates) #1049 (claimed)
• [V3] Improve Concept Exercise: Null and Undefined #1166
• Improve Concept Exercise: Type Conversion (lucky numbers) #1247
• Improve Concept Exercise: Elyses Analytic Enchantments (array-analysis) #1325
• Improve Concept Exercise: Elyses Transformative Enchantments (array-transformations) #1326 (claimed)
• Improve Concept Exercise: Coordinate Transformation (closures) #1373
• Improve Concept Exercise "Fruit Picker": Add Concept arrow-functions #1340
• Improve Concept Exercise "Factory Sensors": Add Concept inheritance #1341
• Improve Concept Exercise: Coordinate Transformation (closures) #1373
• Implement or Improve Concept Exercise: object-destructuring #948
• Improve Concept Exercise: recursion #945
• [exercises/concept/fruit-picker] Exercise requires users to be familiar with the throw statement #1634
• [closures] Concept examples and explanation needs improvements #1529
• Improve Concept Exercise: Functions (Lasagna Master) #1234 (low priority)

There are probably some more issues needed, feel free to create additional ones if you notice problems with existing concept exercises.