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>

Cargo.toml

@@ -61,6 +61,8 @@ once_cell = "1.9.0"
 rayon = "1.5.0"
 component-macro-test = { path = "crates/misc/component-macro-test" }
 wasmtime-wast = { path = "crates/wast", version = "=0.40.0", features = ['component-model'] }
+component-test-util = { path = "crates/misc/component-test-util" }
+wasmtime-component-util = { path = "crates/component-util" }
 
 [target.'cfg(windows)'.dev-dependencies]
 windows-sys = { version = "0.36.0", features = ["Win32_System_Memory"] }
@@ -110,7 +112,11 @@ memory-init-cow = ["wasmtime/memory-init-cow", "wasmtime-cli-flags/memory-init-c
 pooling-allocator = ["wasmtime/pooling-allocator", "wasmtime-cli-flags/pooling-allocator"]
 all-arch = ["wasmtime/all-arch"]
 posix-signals-on-macos = ["wasmtime/posix-signals-on-macos"]
-component-model = ["wasmtime/component-model", "wasmtime-wast/component-model", "wasmtime-cli-flags/component-model"]
+component-model = [
+  "wasmtime/component-model",
+  "wasmtime-wast/component-model",
+  "wasmtime-cli-flags/component-model"
+]
 
 # Stub feature that does nothing, for Cargo-features compatibility: the new
 # backend is the default now.