Add initial support for code metadata (#1840)

See https://github.com/WebAssembly/tool-conventions/blob/main/CodeMetadata.md  for the specification.

In particular this pr implements the following:

- Parsing code metadata sections in BinaryReader, providing appropriate callbacks that a BinaryReaderDelegate can implement:
    - BinaryReaderObjdump: show the sections in a human-readable form
    - BinaryReaderIr: add code metadata in the IR as expressions
- Parsing code metadata annotations in text format, adding them in the IR like the BinaryReaderIR does
- Writing the code metadata present in the IR in the proper sections when converting IR to binary
- Support in wasm-decompiler for showing code metadata as comments in the pseudo-code

All the features have corresponding tests.

Support for code metadata is gated through the --enable-code-metadata feature. For reading/writing in the text format, --enable-annotations is also required.

Missing features:

    Support for function-level code metadata (offset 0)
    Extensive validation in validator.cc (like making sure that all metadata instances are at the same code offset of an instruction)

1 files changed, 6 insertions, 0 deletions

diff --git a/src/decompiler.cc b/src/decompiler.cc
index 1ddaedc3..91272301 100644
--- a/src/decompiler.cc
+++ b/src/decompiler.cc
@@ -604,6 +604,12 @@ struct Decompiler {
         ts += "](";
         return WrapChild(args[0], ts, ")", Precedence::Atomic);
       }
+      case ExprType::CodeMetadata: {
+        auto cme = cast<CodeMetadataExpr>(n.e);
+        std::string c = "// @metadata.code." + cme->name + " ";
+        c += BinaryToString(cme->data);
+        return Value{{std::move(c)}, Precedence::None};
+      }
       default: {
         // Everything that looks like a function call.
         std::string name;