Fix enchantment init

[Doc94]

Fixs #11623 like Tags enchantments (and pretty sure many other Registry things) can be removed by datapacks and how CrafBukkit (for legacy) expects vanilla ever exists can cause issues...
This PR just make the Vanillla Enchantments can be null in the Bukkit Enchantment class also mention in docs about this (more "easy" than add Nullable to all the static instances of Enchantment with the same issue (or maybe this can be better)

[electronicboy]

This is potentially going to be fun if nothing is expecting those fields to be nullable, but, the reality here is that this is somewhat unavoidable

[kennytv]

There is one concern that removing enchantments will break even in vanilla somewhere down the line, as is the case with many other client synchronized registries making the client crash once it does try to reference individual ones somewhere in game logic

[Doc94]

There is one concern that removing enchantments will break even in vanilla somewhere down the line, as is the case with many other client synchronized registries making the client crash once it does try to reference individual ones somewhere in game logic

hmm exists a form to check this? i mean the datapack allow make this in vanilla if a issue happen is more a report for the MOJIRA? if they allow make this

[kennytv]

Okay for enchantments specifically I don't see such use, so it might be okay to remove them as long as all loot tables etc. that reference the enchantments are removed by the datapack? but it makes for weird api here, if we merge this we just have to make sure it's very clear they can be null

[lynxplay]

At least my two cents on this.
Given we cannot expand this to all data driven types (see damage type), I am unsure if pulling such a move is smart for our API as the Enchantment value would be the only one that could be null.

Additionally, removing vanilla enchants is also a rather edge-case imo.
You still have to manually remove from them from everything else so I think the workaround of "remove them from everywhere but the registry" is a fine one to make to preserve the API here.

More opinions obviously needed tho.