Major cleanup. Remove compile, compile_wasm, and MixTape

[MasonProtter]

This removes the compile functionality (closes #119), and does some general cleanup and fixes.

Before we merge this though, I'd also like to also discuss removing

• the Mixtape stuff since I'm not really convinced it's worth the maintenance burden when we already have @device_override which is easier to use, and doesn't rely on the broken, unmaintained CodeInfoTools.jl. @device_override should cover every reasonable usecase as far as I'm aware.
• The wasm stuff because https://github.com/tshort/WebAssemblyCompiler.jl exists and appears to work, whereas I'm not sure the wasm stuff in here works or not. Alternative we could look at bringing the functionality from that package in to here. cc @tshort

[MasonProtter]

Failing integration tests appear to be because of wasm.

[tshort]

Thumbs up on this PR. I looked over the code, but I didn't really do a code review. If it passes tests, I'm good.

I'm okay with removing both the Mixtape and the wasm support. For wasm, I think WebAssemblyCompiler will (should) compile more code and offer more capability. I agree that the @device_override is way easier than Mixtape. For code I'm using (mainly WebAssemblyCompiler), I've used the overlays a lot but haven't needed Mixtape.

[tshort]

As part of the cutting of features, I would like to keep the cross-compiling support.

[brenhinkeller]

This looks good to me! This package has really come a long way and taught us all a lot I think. This slimming-down should be great for the maintenance burden going forward, and anyone can always check out the older versions if they want to see all the other things we experimented with.

I'm happy with merging whenever it seems like tests are in as good shape as we can get them, as long as Tom's happy too

[MasonProtter]

Okay, I've removed the wasm stuff, and the mixtape stuff. I also added an ability to specify your own method_table during compilation, in case there are cases where someone wants to do a certain overload just for a certain function they want to compile, but don't want to pollute the StaticCompiler wider method-table.

[brenhinkeller]

Hooray!