Move seahorse_util to separate file

[z80dev]

this makes the generated lib.rs much easier to read

it also sets a pattern for adding future library files as needed.

[mcintyre94]

This seems like a good idea! I just want to make sure it'll still work with Solana Playground

Can you give a bit more detail on what this changes about the output files?

[z80dev]

Seahorse generates what is essentially a regular valid Anchor Rust project to be compiled by the Anchor CLI. Currently, all the code is thrown into a single lib.rs file. This includes code that is in a module seahorse_util. This module contains a bunch of seahorse boilerplate, helper functions, and traits for properly generating valid working Rust code from the python source.

This Seahorse boilerplate clutters the lib.rs file unnecessarily, it is trivial to put it in an adjacent file and then just "import" it via use. An additional benefit is that this makes it easier to test that Seahorse outputs are correct, since we now can generate much smaller and simpler lib.rs files that do not include all the Seahorse boilerplate.

I haven't ever used the Solana playground but I'll take a look and respond with more thoughts once I do