PHP Node: Only consider NODEFS to be a shared filesystem

[adamziel]

Motivation for the change, related issues

#2231 overrides FS.hashAddNode with function hashAddNodeIfNotSharedFS(node) where additional logic applies if is_shared_fs_node(node) is true. Only NODEFS nodes were supposed to be considered as coming from a shared fs. Unfortunately, the internal logic of is_shared_fs_node() also returned true for MEMFS nodes. This caused a FS error 44 for the following operation where runtime2 attempts to create a directory in a /wordpress directory mounted from runtime1:

import { loadNodeRuntime } from "@php-wasm/node";
import { getLoadedRuntime } from "@php-wasm/universal";

const opts = {
	emscriptenOptions: { ENV: { DOCROOT: '/wordpress' } }
};
const runtime1 = getLoadedRuntime(await loadNodeRuntime('8.3', opts));
runtime1.FS.mkdir("/wordpress");

const runtime2 = getLoadedRuntime(await loadNodeRuntime('8.3', opts));
runtime2.FS.mkdir("/wordpress");

runtime2.FS.mount(
	runtime2.PROXYFS,
	{ root: '/wordpress', fs: runtime1.FS },
	'/wordpress'
);

// This works:
// runtime1.FS.mkdir("/wordpress/wp-content");

// This doesn't:
runtime2.FS.mkdir("/wordpress/wp-content");

Specifically, the FS error 44 was triggered inside is_shared_fs_node() when calling NODEFS operations on these non-NODEFS nodes.

Implementation details

Adds a check confirming the shared node comes from NODEFS.

Testing Instructions (or ideally a Blueprint)

• Confirm the reproduction above works without errors.
• Once [ php-wasm ] Add test-unit-jspi in CI workflow #2285 lands, we'll be able to add a unit test

cc @brandonpayton

[adamziel]

I'll go ahead and merge to unblock #2281. We can always revert if something's off here