Remove tokio dependency

[Spaceface16518]

Substituted with a manually chunked std::thread approach. While this does use a different dependency, it's significantly less dependencies overall.

Currently, this decreases performance by a couple milliseconds on my machine, but hopefully I will fix this in the next few commits. I'm going to create some benchmarks to calculate the best buffer size for the channel as well.

[abour]

Hi Spaceface16518. Thank you for your merge request. I'm 100% open to remove the tokio dependency but I'll not do it while it decreases the performance. By the way, I received a comment on the reddit thread that mention a 60% performance boost with a simple modification. That could be an interesting approach to evaluate: https://www.reddit.com/r/rust/comments/jyziio/a_fractal_i_rendered_with_rust_without_any/gd8xvl2?utm_source=share&utm_medium=web2x&context=3

[Spaceface16518]

I'm 100% open to remove the tokio dependency but I'll not do it while it decreases the performance.

I agree, I'm working on performance right now.

By the way, I received a comment on the reddit thread that mention a 60% performance boost with a simple modification. That could be an interesting approach to evaluate: https://www.reddit.com/r/rust/comments/jyziio/a_fractal_i_rendered_with_rust_without_any/gd8xvl2?utm_source=share&utm_medium=web2x&context=3

This change uses the rayon library. While it would be a lighter dependency than tokio (tokio itself depends on rayon) but I still feel like avoiding dependencies that do everything for you is a goal here (even if the Go standard library does everything for you).