Add max level evolution with Rare Candy

MR Description

• Starting from gen 8 games (Sword & Shield), a Rare Candy can be used on a max level Pokémon if they evolve by level. For instance, a level 100 Magikarp couldn't legally evolve before gen 8. Afterwards, it would be able to evolve by using a Rare Candy.

Before testing

• Get yourself a max level Pokémon that can evolve.

Notes to acknowledge before testing

• I've put the evolution process in the loop, so a Pokémon that can evolve multiple times will, if a multiple levels increasing item is used. (For example, the usage of a single rare candy that would give 2 levels to a level 100 Turtwig would make it evolve twice.)
• In Gen 9 onwards, the Rare Candy isn't consumed if the Pokémon hasn't levelled up. I haven't implemented that.

Tests to realize

• Try evolving a max level'd Pokémon with a rare candy.
• (Optional) Make sure it can't evolve otherwise.

Sources related to this MR

• Bulbapedia link
• Pokepedia link