Convert the streaming server to ESM (#29389)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

streaming/.eslintrc.cjs

@@ -0,0 +1,43 @@
+/* eslint-disable import/no-commonjs */
+
+// @ts-check
+
+// @ts-ignore - This needs to be a CJS file (eslint does not yet support ESM configs), and TS is complaining we use require
+const { defineConfig } = require('eslint-define-config');
+
+module.exports = defineConfig({
+  extends: ['../.eslintrc.js'],
+  env: {
+    browser: false,
+  },
+  parserOptions: {
+    project: true,
+    tsconfigRootDir: __dirname,
+    ecmaFeatures: {
+      jsx: false,
+    },
+    ecmaVersion: 2021,
+  },
+  rules: {
+    // In the streaming server we need to delete some variables to ensure
+    // garbage collection takes place on the values referenced by those objects;
+    // The alternative is to declare the variable as nullable, but then we need
+    // to assert it's in existence before every use, which becomes much harder
+    // to maintain.
+    'no-delete-var': 'off',
+
+    // This overrides the base configuration for this rule to pick up
+    // dependencies for the streaming server from the correct package.json file.
+    'import/no-extraneous-dependencies': [
+      'error',
+      {
+        devDependencies: ['streaming/.eslintrc.cjs'],
+        optionalDependencies: false,
+        peerDependencies: false,
+        includeTypes: true,
+        packageDir: __dirname,
+      },
+    ],
+    'import/extensions': ['error', 'always'],
+  },
+});