[eslint] move rest of repository to eslint flat config

***NO_CI***

- Add a centralized eslint flat config

sdk/eslint.config.mjs

@@ -0,0 +1,3 @@
+import azsdkEslint from "../common/tools/eslint-plugin-azure-sdk/dist-esm/src/index.js";
+
+export default [...azsdkEslint.configs.recommended];