Fix feature-gating of test-programs (#612)

* Fix feature-gating of test-programs

This commit fixes bugs in enabling feature-gating of `test-programs`
which was introduced in #600. It turns out, #600 accidentally
disabled `test-programs` from ever running, and this commit fixes
that.

* Fix the CI

crates/test-programs/tests/wasm_tests/main.rs

@@ -1,4 +1,4 @@
-#![cfg(features = "test-programs")]
+#![cfg(feature = "test_programs")]
 mod runtime;
 mod utils;