add ComponentType/Lift/Lower derive macro for record types (bytecodea…

…lliance#4337)

This is the first stage of implementing
bytecodealliance#4308, i.e. derive macros for
`ComponentType`, `Lift`, and `Lower` for composite types in the component model.
This stage only covers records; I expect the other composite types will follow a
similar pattern.

It borrows heavily from the work Jamey Sharp did in
bytecodealliance#4217.  Thanks for that, and
thanks to both Jamey and Alex Crichton for their excellent review feedback.
Thanks also to Brian for pairing up on the initial draft.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

crates/component-macro/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "wasmtime-component-macro"
+version = "0.39.0"
+authors = ["The Wasmtime Project Developers"]
+description = "Macros for deriving component interface types from Rust types"
+license = "Apache-2.0 WITH LLVM-exception"
+repository = "https://github.com/bytecodealliance/wasmtime"
+documentation = "https://docs.rs/wasmtime-component-macro/"
+categories = ["wasm"]
+keywords = ["webassembly", "wasm"]
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0", features = ["extra-traits"] }
+
+[badges]
+maintenance = { status = "actively-developed" }