Output structured data format based on wasm-delegations.def

[phated]

Based on https://github.com/WebAssembly/binaryen/discussions/6225#discussioncomment-8954759

Currently, many Wasm instructions are defined in src/wasm-delegations*.def, which is a C header that Binaryen and tools within Binaryen can use.

This file could also be processed and output as structured data (JSON, YAML, etc) in the build artifacts, which would allow other tools and bindings to consume it for automation.

I'm particular to JSON, but we should see what others would want to consume.

[kripken]

I opened #6469 for this, let me know what you think there.