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>

fuzz/Cargo.toml

@@ -9,6 +9,8 @@ publish = false
 cargo-fuzz = true
 
 [dependencies]
+anyhow = { version = "1.0.19" }
+arbitrary = { version = "1.1.0", features = ["derive"] }
 cranelift-codegen = { path = "../cranelift/codegen" }
 cranelift-reader = { path = "../cranelift/reader" }
 cranelift-wasm = { path = "../cranelift/wasm" }
@@ -19,6 +21,16 @@ libfuzzer-sys = "0.4.0"
 target-lexicon = "0.12"
 wasmtime = { path = "../crates/wasmtime" }
 wasmtime-fuzzing = { path = "../crates/fuzzing" }
+component-test-util = { path = "../crates/misc/component-test-util" }
+component-fuzz-util = { path = "../crates/misc/component-fuzz-util" }
+
+[build-dependencies]
+anyhow = "1.0.19"
+proc-macro2 = "1.0"
+arbitrary = { version = "1.1.0", features = ["derive"] }
+rand = { version = "0.8.0" }
+quote = "1.0"
+component-fuzz-util = { path = "../crates/misc/component-fuzz-util" }
 
 [features]
 default = ['fuzz-spec-interpreter']
@@ -102,3 +114,9 @@ name = "instantiate-many"
 path = "fuzz_targets/instantiate-many.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "component_api"
+path = "fuzz_targets/component_api.rs"
+test = false
+doc = false