Add *.wast support for invoking components (#4526)

This commit builds on bytecodealliance/wasm-tools#690 to add support to
testing of the component model to execute functions when running
`*.wast` files. This support is all built on #4442 as functions are
invoked through a "dynamic" API. Right now the testing and integration
is fairly crude but I'm hoping that we can try to improve it over time
as necessary. For now this should provide a hopefully more convenient
syntax for unit tests and the like.

crates/test-programs/Cargo.toml

@@ -20,7 +20,7 @@ pretty_env_logger = "0.4.0"
 tempfile = "3.1.0"
 os_pipe = "0.9"
 anyhow = "1.0.19"
-wat = "1.0.45"
+wat = "1.0.47"
 cap-std = "0.25.0"
 tokio = { version = "1.8.0", features = ["rt-multi-thread"] }