Stop using cargo-make for all workflows

[Lokathor]

I think that, on balance, we should adjust the repo to stop using cargo make as our default build flow.

1. We can use .cargo/config.toml to specify a default target, and to specify build-std=core.
2. mgba can just execute the ELF format binaries directly during testing.

The reason that I bring this up is because using cargo-make to specify those things instead of having them in the .cargo/config.toml file actually kinda messes up Rust Analyzer. I'd prefer that Rust Analyzer works well, and the final "releasing" of a ROM is maybe a step or two more complicated, instead of the other way around.

however, this probably affects several others besides myself, so I'm opening an issue about it to see what people think.