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/fuzzing/Cargo.toml

@@ -10,6 +10,8 @@ license = "Apache-2.0 WITH LLVM-exception"
 [dependencies]
 anyhow = "1.0.22"
 arbitrary = { version = "1.1.0", features = ["derive"] }
+component-test-util = { path = "../misc/component-test-util" }
+component-fuzz-util = { path = "../misc/component-fuzz-util" }
 env_logger = "0.9.0"
 log = "0.4.8"
 rayon = "1.2.1"