Breaking: new Polyscript Hooks mechanism (#1811)

* Breaking: new Polyscript Hooks mechanism

* Added proper smoke test

pyscript.core/src/plugins-helper.js

@@ -0,0 +1,26 @@
+import { defineProperty } from "polyscript/exports";
+
+// helper for all script[type="py"] out there
+const before = (script) => {
+    defineProperty(document, "currentScript", {
+        configurable: true,
+        get: () => script,
+    });
+};
+
+const after = () => {
+    delete document.currentScript;
+};
+
+// common life-cycle handlers for any node
+export default async (main, wrap, element, hook) => {
+    const isAsync = hook.endsWith("Async");
+    const isBefore = hook.startsWith("onBefore");
+    // make it possible to reach the current target node via Python
+    // or clean up for other scripts executing around this one
+    (isBefore ? before : after)(element);
+    for (const fn of main(hook)) {
+        if (isAsync) await fn(wrap, element);
+        else fn(wrap, element);
+    }
+};