Implement DataCountSection and ExceptionSection parsing

[Jacarte]

Add the decoding/encoding of sections 12 and 13 (DataCountSection and ExceptionSection).

Here we can find the reference implementation in V8

[Jacarte]

https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md

[monperrus]

This prevents us to parse with SWAM the binary of FFMPEG compiled to WASM, link to come.

[Jacarte]

Example wasm ffmpeg