fix(codegen): Reverts & Disables codegen (for now) (#625)

After speaking with the C# devs, it is clear that code gen is not ready.
I can get around this by doing the following:
1. Creating a library
2. Splitting out the schema writing from the source generator
3. Moving the schema loading to `AdditionalFiles`
4. Writing a new post-build application using Roslyn to write the schema files after building.

Projects/UOContent/Migrations/Server.Items.WrappedCandy.v0.json

@@ -1,5 +0,0 @@
-{
-  "version": 0,
-  "type": "Server.Items.WrappedCandy",
-  "properties": []
-}