Discrepancy in binary representation of future and error-context

[cpetig]

Probably because WebAssembly/component-model#384 was merged a few weeks before WebAssembly/component-model#405 , the component model binary specification defines futures as 0x65 and error-contexts as 0x64.

Wasm-tools on the other hand uses future 0x67 and error-context 0x65. I guess the implementation predates the spec.

Both agree on streams as 0x66.

I can create a PR to make wasm-tools follow the spec, but I would like to clarify that this is indeed the right path.

PS: I found this problem while implementing fixed size lists in #1992 ...

[alexcrichton]

Fixed in #2045