remove testsuite-generated from source control

[marler8997]

Builds wast2json using the upstream WebAssembly source and some build.zig and uses that to generate the testsuite json files on demand.

Tested on macOS/Windows and linux.

[malcolmstill]

@marler8997 this is great, love the approach of building wast2json from source (which nicely solves why I added the blobs in the first place, which if I recall correctly was to avoid depending on the tools via apt get).

[malcolmstill]

Also I've changed the repo settings so the CI should kick in now automatically if you make a PR

[marler8997]

Looks like the parsecheck step/tool were validating the wasm binaries commited to the repo that were the output of wast2json? If so, we could probably remove this step/tool since the testsuite itself would validate the output correct?

[malcolmstill]

@marler8997 I'm trying to understand why parsecheck was added in the first place; from #168 looks like it was maybe for testing that parsing never crashes (even for features that were yet to be supported) and I also see that it I was saving .wasm blobs that I had generated through fuzz testing that had highlighted bugs in the parser.

I'll have a think about that latter point (of the fuzzed examples) and maybe you can let me know your thoughts, but I'm happy to just remove this code for the moment (it's a trivial amount of code)