refactor: update to use ristretto_classfile crate to generate Java byte code

[brianheineman]

Really exciting project! I thought you might find a crate I wrote useful for this project. This crate should make it easier to generate the byte code by automatically handling the constant pool offsets for long/double, as well translate logical instruction pointers to byte code offsets, etc.

[IntegralPilot]

Thank you so much for making your amazing crate and for helping me integrate it, this code is much cleaner now! All tests pass locally, so I'm going to merge this. Thanks again! :)

[brianheineman]

@IntegralPilot I'm glad you find it helpful! I realized that I should be providing a means to calculate the max_stack and max_locals as well. I put together a PR to address calculating the max_stack size; I'll try to get that released soon and submit another PR that will hopefully simplify a bit more for you: theseus-rs/ristretto#295, theseus-rs/ristretto#296, theseus-rs/ristretto#300