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>

tests/all/component_model/dynamic.rs

@@ -1,19 +1,8 @@
 use super::{make_echo_component, make_echo_component_with_params, Param, Type};
 use anyhow::Result;
-use wasmtime::component::{self, Component, Func, Linker, Val};
-use wasmtime::{AsContextMut, Store};
-
-trait FuncExt {
-    fn call_and_post_return(&self, store: impl AsContextMut, args: &[Val]) -> Result<Val>;
-}
-
-impl FuncExt for Func {
-    fn call_and_post_return(&self, mut store: impl AsContextMut, args: &[Val]) -> Result<Val> {
-        let result = self.call(&mut store, args)?;
-        self.post_return(&mut store)?;
-        Ok(result)
-    }
-}
+use component_test_util::FuncExt;
+use wasmtime::component::{self, Component, Linker, Val};
+use wasmtime::Store;
 
 #[test]
 fn primitives() -> Result<()> {