Previously, wasm-pack was hardcoded to install and attempt to execute wasm-opt on every build
using binaryen version 78. This version had various issues on Unix/Linux and caused broken CI
builds for many folks (we're so sorry!).
This PR updates the binaryen version to 90, which should fix the issues folks were having.
Long-term, we'd like to create an auto-updating mechanism so that we can install and use the
latest release of binaryen as we do for other binaries we orchestrate.