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/environ/fuzz/Cargo.toml

@@ -15,6 +15,7 @@ libfuzzer-sys = "0.4"
 wasmparser = "0.88.0"
 wasmprinter = "0.2.37"
 wasmtime-environ = { path = ".." }
+component-fuzz-util = { path = "../../misc/component-fuzz-util", optional = true }
 
 [[bin]]
 name = "fact-valid-module"
@@ -24,4 +25,4 @@ doc = false
 required-features = ["component-model"]
 
 [features]
-component-model = ["wasmtime-environ/component-model"]
+component-model = ["wasmtime-environ/component-model", "dep:component-fuzz-util"]