Generate the forwarder NCAs entirely in JavaScript

[TooTallNate]

It should be relatively straightforward to bypass hacbrewpack and implement the NCA generation logic in JavaScript. This would be a lot faster and make nsp-forwarder.nro smaller, since it would not need to go through the emscripten-compiled WASM binary execution.

@ITotalJustice's implementation is the most noteworthy: https://github.com/ITotalJustice/sphaira/blob/0370e47f7fac0e426675624f363fe50f3b442048/sphaira/source/owo.cpp

[ITotalJustice]

It doesn't generate a nsp fwiw. A nsp is just a packed file with subfiles inside, exactly like a zip files with no compression.

Sphaira generates ncas and installs them directly. Nsps are only needed for title installers.