Refactor the source generator to be public

The compiler is not able to infer the generics types when using constraints. For this reason, a source generator was used to generate all the generics mappings so that a developer doesn't have to explicitly specify the types when calling each operation. The source generator was an internal project, executed before packaging the library.

This refactoring changes the source generator to be publicly distributed and executed when compiling the projects that depend on Hyperlinq. It will only generate the overloads required by the project.

This refactoring is necessary because it's very hard to map the generics types in the way it was done. When executing on the project, the explicit types have already been declared. This makes the source generator much simpler, allows the generation of a lot less code. It can also perform more optimizations.