Add a wasmtime::component::bindgen! macro (#5317)

* Import Wasmtime support from the `wit-bindgen` repo

This commit imports the `wit-bindgen-gen-host-wasmtime-rust` crate from
the `wit-bindgen` repository into the upstream Wasmtime repository. I've
chosen to not import the full history here since the crate is relatively
small and doesn't have a ton of complexity. While the history of the
crate is quite long the current iteration of the crate's history is
relatively short so there's not a ton of import there anyway. The
thinking is that this can now continue to evolve in-tree.

* Refactor `wasmtime-component-macro` a bit

Make room for a `wit_bindgen` macro to slot in.

* Add initial support for a `bindgen` macro

* Add tests for `wasmtime::component::bindgen!`

* Improve error forgetting `async` feature

* Add end-to-end tests for bindgen

* Add an audit of `unicase`

* Add a license to the test-helpers crate

* Add vet entry for `pulldown-cmark`

* Update publish script with new crate

* Try to fix publish script

* Update audits

* Update lock file

crates/component-macro/Cargo.toml

@@ -12,12 +12,24 @@ edition.workspace = true
 
 [lib]
 proc-macro = true
+test = false
+doctest = false
 
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
 syn = { version = "1.0", features = ["extra-traits"] }
 wasmtime-component-util = { workspace = true }
+wasmtime-wit-bindgen = { workspace = true }
+wit-parser = { workspace = true }
 
 [badges]
 maintenance = { status = "actively-developed" }
+
+[dev-dependencies]
+wasmtime = { path = '../wasmtime', features = ['component-model'] }
+component-macro-test-helpers = { path = 'test-helpers' }
+tracing = { workspace = true }
+
+[features]
+async = []