Elastic scaling: add e2e test (#3929)

On top of https://github.com/paritytech/polkadot-sdk/pull/3879

I've also moved the previous test where we ensure multiple cores per
para doesn't break non elastic parachains.

---------

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
Co-authored-by: Javier Viola <363911+pepoviola@users.noreply.github.com>

polkadot/zombienet_tests/elastic_scaling/assign-core.js

@@ -0,0 +1,41 @@
+async function run(nodeName, networkInfo, args) {
+  const { wsUri, userDefinedTypes } = networkInfo.nodesByName[nodeName];
+  const api = await zombie.connect(wsUri, userDefinedTypes);
+
+  let para = Number(args[0]);
+  let core = Number(args[1]);
+  console.log(`Assigning para ${para} to core ${core}`);
+
+  await zombie.util.cryptoWaitReady();
+
+  // account to submit tx
+  const keyring = new zombie.Keyring({ type: "sr25519" });
+  const alice = keyring.addFromUri("//Alice");
+
+  await new Promise(async (resolve, reject) => {
+    const unsub = await api.tx.sudo
+      .sudo(api.tx.coretime.assignCore(core, 0, [[{ task: para }, 57600]], null))
+      .signAndSend(alice, ({ status, isError }) => {
+        if (status.isInBlock) {
+          console.log(
+            `Transaction included at blockhash ${status.asInBlock}`,
+          );
+        } else if (status.isFinalized) {
+          console.log(
+            `Transaction finalized at blockHash ${status.asFinalized}`,
+          );
+          unsub();
+          return resolve();
+        } else if (isError) {
+          console.log(`Transaction error`);
+          reject(`Transaction error`);
+        }
+      });
+  });
+
+
+
+  return 0;
+}
+
+module.exports = { run };