wasi: rename __wasi_unstable_reactor_start()

Upstream WASI has renamed __wasi_unstable_reactor_start() to
_initialize(). This commit updates Node's WASI implementation to
reflect that change.

PR-URL: #33073
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gus Caplan <me@gus.host>

doc/api/wasi.md

@@ -72,8 +72,8 @@ added: v12.16.0
 
 Attempt to begin execution of `instance` by invoking its `_start()` export.
 If `instance` does not contain a `_start()` export, then `start()` attempts to
-invoke the `__wasi_unstable_reactor_start()` export. If neither of those exports
-is present on `instance`, then `start()` does nothing.
+invoke the `_initialize()` export. If neither of those exports is present on
+`instance`, then `start()` does nothing.
 
 `start()` requires that `instance` exports a [`WebAssembly.Memory`][] named
 `memory`. If `instance` does not have a `memory` export an exception is thrown.

lib/wasi.js

@@ -96,8 +96,8 @@ class WASI {
     try {
       if (exports._start)
         exports._start();
-      else if (exports.__wasi_unstable_reactor_start)
-        exports.__wasi_unstable_reactor_start();
+      else if (exports._initialize)
+        exports._initialize();
     } catch (err) {
       if (err !== kExitCode) {
         throw err;

test/wasi/test-wasi-start-validation.js

@@ -83,7 +83,7 @@ const bufferSource = fixtures.readSync('simple.wasm');
     get() {
       return {
         memory: new WebAssembly.Memory({ initial: 1 }),
-        __wasi_unstable_reactor_start: common.mustCall()
+        _initialize: common.mustCall()
       };
     }
   });