Reorganize wasi-misc-tests. (#575)

* Reorganize wasi-misc-tests.

Move wasi-misc-tests out of wasi-common, to break a dependency cycle;
previously, wasmtime-* depended on wasi-common, but wasi-common
dev-dependended on wasmtime-*.

Now, wasi-common no longer dev-depends on wasmtime-*; instead, the
tests are in their own crate which depends on wasi-common and on
wasmtime-*.

Also, rename wasi-misc-tests to wasi-tests for simplicity.

This also removes the "wasm_tests" feature; it's replaced by the
"test-programs" feature.

* Update the CI script to use the new feature name.

* Update the CI script to use the new feature name in one more place.

* Change a `write!` to a `writeln!`.

Cargo.toml

@@ -41,6 +41,10 @@ libc = "0.2.60"
 rayon = "1.1"
 wasm-webidl-bindings = "0.6"
 more-asserts = "0.2.1"
+# This feature requires the wasm32-wasi target be installed. It enables
+# wasm32-wasi integration tests. To enable, run
+# `cargo test --features test-programs`.
+test-programs = { path = "crates/test-programs", optional = true }
 
 [build-dependencies]
 anyhow = "1.0.19"
@@ -51,8 +55,6 @@ members = [
   "crates/misc/py",
 ]
 
-exclude = ["crates/wasi-common/wasi-misc-tests"]
-
 [features]
 lightbeam = [
     "wasmtime-environ/lightbeam",