Add a pure Wasm image classification benchmark

[adambratschikaye]

Add a benchmark which performs image classification in pure Wasm using tract and ONNX. This can be useful to track the performance of float heavy computations.

[adambratschikaye]

I think the rebuild failure is due to libsodium now requiring zig 0.12, but the Dockerfile uses zig 0.10.1.

[adambratschikaye]

Rebuild failure should be fixed in #271

[jlb6740]

An assets directory needs to be created first.

[adambratschikaye]

Oops, thanks I'll fix that.

[jlb6740]

@adambratschikaye I was not familiar with tract but was introduced by your issue here: bytecodealliance/wasmtime#8313, so thanks for submitting. I think getting this in now is great but ultimately maybe this directory could be refactored to include multiple inferencing scenarios.

[adambratschikaye]

I'm not exactly sure what's up with the current failure. It looks like the mac tests are failing with:

stderr=```" INFO  sightglass_cli::benchmark > Using benchmark engine:
/Users/runner/work/sightglass/sightglass/engines/wasmtime/libengine.dylib
Error: dlopen(/Users/runner/work/sightglass/sightglass/engines/wasmtime/libengine.dylib, 0x0005): tried: \'/Users/runner/work/sightglass/sightglass/engines/wasmtime/libengine.dylib\' (mach-o file, but is an incompatible architecture (have \'x86_64\', need \'arm64e\' or \'arm64\')),
\'/System/Volumes/Preboot/Cryptexes/OS/Users/runner/work/sightglass/sightglass/engines/wasmtime/libengine.dylib\' (no such file),
\'/Users/runner/work/sightglass/sightglass/engines/wasmtime/libengine.dylib\' (mach-o file, but is an incompatible architecture (have \'x86_64\', need \'arm64e\' or \'arm64\'))
Error: benchmark subprocess did not exit successfully\n"```

so maybe something is up with the cached wasmtime engine for mac?

[jlb6740]

@adambratschikaye Looks like you were right. Not sure the corruption, but it was using an incorrect cached version of the wasmtime-engine. I removed the cached image for macos and reran so that it had to build again, and now all tests pass.