implement fuzzing for component types (#4537)

This addresses #4307.

For the static API we generate 100 arbitrary test cases at build time, each of
which includes 0-5 parameter types, a result type, and a WAT fragment containing
an imported function and an exported function.  The exported function calls the
imported function, which is implemented by the host.  At runtime, the fuzz test
selects a test case at random and feeds it zero or more sets of arbitrary
parameters and results, checking that values which flow host-to-guest and
guest-to-host make the transition unchanged.

The fuzz test for the dynamic API follows a similar pattern, the only difference
being that test cases are generated at runtime.

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

crates/misc/component-fuzz-util/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "component-fuzz-util"
+authors = ["The Wasmtime Project Developers"]
+license = "Apache-2.0 WITH LLVM-exception"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+anyhow = { version = "1.0.19" }
+arbitrary = { version = "1.1.0", features = ["derive"] }
+proc-macro2 = "1.0"
+quote = "1.0"
+wasmtime-component-util = { path = "../../component-util" }