Implement a composition graph library.

This commit implements a composition graph library that will serve as the basis
for how WAC does AST resolution in the near future.

The inspiration comes from the existing `CompositionGraph` API in
`wasm-compose`, except this API is more flexible, allowing a composition graph
to define its own types, have explicit exports, and export any node in the
graph.

The type representation present in `wac-parser` has been extracted to its own
crate, `wac-types`. It will be shared in the future between the parser and the
graph library.

As a result, a chunk of this new code is just copied out of `wac-parser`. Once
the graph library is merged, a follow-up commit will eliminate the duplicated
code and change `wac-parser` to resolve ASTs to a `CompositionGraph`.

Author: peterhuene

Cargo.lock

@@ -47,6 +47,8 @@ registry = ["wac-resolver/registry", "indicatif"]
 [workspace.dependencies]
 wac-parser = { path = "crates/wac-parser", default-features = false }
 wac-resolver = { path = "crates/wac-resolver", default-features = false }
+wac-graph = { path = "crates/wac-graph" }
+wac-types = { path = "crates/wac-types" }
 wit-parser = "0.201.0"
 wasmparser = "0.201.0"
 wit-component = "0.201.0"
@@ -77,3 +79,4 @@ secrecy = "0.8.0"
 futures = "0.3.30"
 indicatif = "0.17.8"
 pretty_assertions = "1.4.0"
+petgraph = "0.6.4"

Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+name = "wac-graph"
+description = "A library for defining, encoding, and decoding WebAssembly composition graphs."
+version = { workspace = true }
+edition = { workspace = true }
+authors = { workspace = true }
+license = { workspace = true }
+categories = { workspace = true }
+keywords = { workspace = true }
+repository = { workspace = true }
+
+[dependencies]
+wac-types = { workspace = true }
+id-arena = { workspace = true }
+anyhow = { workspace = true }
+thiserror = { workspace = true }
+petgraph = { workspace = true }
+indexmap = { workspace = true }
+wasmparser = { workspace = true }
+semver = { workspace = true }
+serde = { workspace = true, optional = true }
+wasm-encoder = { workspace = true }
+log = { workspace = true }
+
+[dev-dependencies]
+pretty_assertions = { workspace = true }
+wasmprinter = { workspace = true }
+wat = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+
+[features]
+serde = ["dep:serde", "wac-types/serde"]