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, 17 insertions, 0 deletions

diff --git a/test/decompile/code-metadata.txt b/test/decompile/code-metadata.txt
new file mode 100644
index 00000000..1efd9d65
--- /dev/null
+++ b/test/decompile/code-metadata.txt
@@ -0,0 +1,17 @@
+;;; TOOL: run-wasm-decompile
+
+(module
+  (func $f (param i32) (result i32)
+    i32.const 1234
+    local.get 0
+    (@metadata.code.test "aa\01a") i32.add
+    return))
+
+(;; STDOUT ;;;
+function f_a(a:int):int {
+  let t0 = a;
+  // @metadata.code.test "aa\01a";
+  return 1234 + t0;
+}
+
+;;; STDOUT ;;)