Use set in parser scope (#13408)

* chore: rename benchmark

* perf: back parser scope names storage by set

* chore: add benchmark

packages/babel-parser/benchmark/many-let-declarations/1-length-binding.mjs

@@ -0,0 +1,34 @@
+import Benchmark from "benchmark";
+import baseline from "@babel-baseline/parser";
+import current from "../../lib/index.js";
+import { report } from "../util.mjs";
+
+const suite = new Benchmark.Suite();
+// All codepoints in [0x4e00, 0x9ffc] are valid identifier name per Unicode 13
+function createInput(length) {
+  if (length > 0x9ffc - 0x4e00) {
+    throw new Error(
+      `Length greater than ${
+        0x9ffc - 0x4e00
+      } is not supported! Consider modify the \`createInput\`.`
+    );
+  }
+  let source = "";
+  for (let i = 0; i < length; i++) {
+    source += "let " + String.fromCharCode(0x4e00 + i) + ";";
+  }
+  return source;
+}
+function benchCases(name, implementation, options) {
+  for (const length of [256, 512, 1024, 2048]) {
+    const input = createInput(length);
+    suite.add(`${name} ${length} length-1 let bindings`, () => {
+      implementation.parse(input, options);
+    });
+  }
+}
+
+benchCases("baseline", baseline);
+benchCases("current", current);
+
+suite.on("cycle", report).run();