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/tests/codegen/many-arguments.wit

@@ -0,0 +1,51 @@
+interface manyarg {
+  many-args: func(
+    a1: u64,
+    a2: u64,
+    a3: u64,
+    a4: u64,
+    a5: u64,
+    a6: u64,
+    a7: u64,
+    a8: u64,
+    a9: u64,
+    a10: u64,
+    a11: u64,
+    a12: u64,
+    a13: u64,
+    a14: u64,
+    a15: u64,
+    a16: u64,
+  )
+
+  record big-struct {
+    a1: string,
+    a2: string,
+    a3: string,
+    a4: string,
+    a5: string,
+    a6: string,
+    a7: string,
+    a8: string,
+    a9: string,
+    a10: string,
+    a11: string,
+    a12: string,
+    a13: string,
+    a14: string,
+    a15: string,
+    a16: string,
+    a17: string,
+    a18: string,
+    a19: string,
+    a20: string,
+  }
+
+  big-argument: func(x: big-struct)
+}
+
+world the-world {
+  import imports: manyarg
+  export exports: manyarg
+  default export manyarg
+}