Wasmtime 0.19.0 and Cranelift 0.66.0 (#2027)

This commit updates Wasmtime's version to 0.19.0, Cranelift's version to
0.66.0, and updates the release notes as well.

crates/wasi/build.rs

@@ -1,4 +1,4 @@
 fn main() {
-    let wasi_root = std::env::var("DEP_WASI_COMMON_18_WASI").unwrap();
+    let wasi_root = std::env::var("DEP_WASI_COMMON_19_WASI").unwrap();
     println!("cargo:rustc-env=WASI_ROOT={}", wasi_root);
 }