Add `simd.suite`

[abrown]

As discussed in a Cranelift meeting, it would be nice to know which benchmarks are SIMD users. This change adds a simd.suite file that lists the files that contain SIMD instructions. This can be run like:

$ cargo run -- benchmark --engine .../libengine.so benchmarks/simd.suite

There are a couple ways this could be improved, but this may be fine as-is for now:

• simd.suite could get out of date; someone could create a CI check to keep it in-sync with the added files
• someone could really check that the measured section of each benchmark is actually a heavy SIMD user by collecting the instruction mix (e.g., sde)

[abrown]

cc: @alexcrichton, @fitzgen, @jameysharp, @cfallin

[abrown]

I'm going to merge this in hopes that recent Wasmtime changes have fixed the build issues.