Add benchmark for [...set] (#26452)

### What does this PR do?

Adds benchmark for `[...set]`

### How did you verify your code works?

### Results

**Bun 1.3.6** 

```
clk: ~3.77 GHz
cpu: Apple M4 Max
runtime: bun 1.3.6 (arm64-darwin)

benchmark                   avg (min … max) p75   p99    (min … top 1%)
------------------------------------------- -------------------------------
[...set] - integers (10)      51.70 ns/iter  51.16 ns   █▄
                     (45.17 ns … 121.75 ns)  87.65 ns ▁▁██▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - integers (100)    394.07 ns/iter 394.41 ns   █▇▂
                    (378.73 ns … 443.39 ns) 437.51 ns ▂████▆▄▂▁▁▁▁▂▃▃▄▂▂▁▂▁
[...set] - strings (10)       53.86 ns/iter  53.66 ns  █
                     (50.72 ns … 115.85 ns)  89.37 ns ▃█▆▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - strings (100)     422.12 ns/iter 422.80 ns    ▅██▄
                    (392.35 ns … 977.34 ns) 481.31 ns ▂▂▅████▇▃▂▁▂▃▄▄▃▃▁▁▁▁
[...set] - objects (10)       54.07 ns/iter  54.33 ns  █▇
                      (49.83 ns … 98.49 ns)  87.07 ns ▂██▇▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - objects (100)     446.81 ns/iter 441.72 ns  █
                    (397.71 ns … 954.87 ns) 824.61 ns ▂█▃▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
```

**Bun 1.3.7 canary**

```
clk: ~3.82 GHz
cpu: Apple M4 Max
runtime: bun 1.3.7 (arm64-darwin)

benchmark                   avg (min … max) p75   p99    (min … top 1%)
------------------------------------------- -------------------------------
[...set] - integers (10)       4.71 ns/iter   4.62 ns  █▄
                       (3.88 ns … 48.91 ns)  11.42 ns ▂██▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - integers (100)     42.52 ns/iter  42.70 ns    █
                      (35.70 ns … 88.03 ns)  74.86 ns ▃█▂██▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - strings (10)        6.02 ns/iter   5.86 ns       ▇█
                       (3.99 ns … 49.43 ns)   8.89 ns ▁▁▁▁▁▂██▆▃▃▂▁▁▁▁▁▁▁▁▁
[...set] - strings (100)      56.81 ns/iter  55.91 ns    █
                      (48.70 ns … 96.89 ns)  88.48 ns ▁▁▃█▇▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - objects (10)        6.15 ns/iter   6.10 ns       █▃
                       (4.14 ns … 66.32 ns)   9.31 ns ▁▁▁▁▂███▆▅▃▂▁▁▁▁▁▁▁▁▁
[...set] - objects (100)      57.47 ns/iter  56.67 ns    ▆█
                     (47.52 ns … 110.06 ns)  93.39 ns ▁▁▃██▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
```

**Node 24.12.0**

```
clk: ~3.30 GHz
cpu: Apple M4 Max
runtime: node 24.12.0 (arm64-darwin)

benchmark                   avg (min … max) p75   p99    (min … top 1%)
------------------------------------------- -------------------------------
[...set] - integers (10)      28.19 ns/iter  13.03 ns █
                       (10.87 ns … 9.37 µs) 129.01 ns █▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - integers (100)    159.41 ns/iter  96.19 ns █
                       (80.87 ns … 8.42 µs)   1.98 µs █▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - strings (10)       20.13 ns/iter  13.56 ns █
                       (10.92 ns … 3.82 µs) 105.83 ns █▅▂▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - strings (100)     138.56 ns/iter  92.29 ns █
                      (80.63 ns … 10.17 µs)   1.09 µs █▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - objects (10)       16.43 ns/iter  12.40 ns  █
                       (11.07 ns … 5.99 µs)  39.03 ns ▄█▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
[...set] - objects (100)     108.58 ns/iter  97.82 ns  █
                       (80.83 ns … 2.99 µs) 298.93 ns ▂█▅▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
```

**Summary**

```zig
  ┌────────────────┬────────────────┬───────────────┬─────────┐
  │   Benchmark    │ Before (1.3.6) │ After (1.3.7) │ Speedup │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ integers (10)  │ 51.70 ns       │ 4.71 ns       │ 11.0x   │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ integers (100) │ 394.07 ns      │ 42.52 ns      │ 9.3x    │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ strings (10)   │ 53.86 ns       │ 6.02 ns       │ 8.9x    │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ strings (100)  │ 422.12 ns      │ 56.81 ns      │ 7.4x    │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ objects (10)   │ 54.07 ns       │ 6.15 ns       │ 8.8x    │
  ├────────────────┼────────────────┼───────────────┼─────────┤
  │ objects (100)  │ 446.81 ns      │ 57.47 ns      │ 7.8x    │
  └────────────────┴────────────────┴───────────────┴─────────┘
```

bench/snippets/spread-set.mjs

@@ -0,0 +1,20 @@
+// Benchmark for [...set] optimization (WebKit#56539)
+// https://github.com/WebKit/WebKit/pull/56539
+import { bench, run } from "../runner.mjs";
+
+const intSet10 = new Set([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+const intSet100 = new Set(Array.from({ length: 100 }, (_, i) => i));
+const strSet10 = new Set(Array.from({ length: 10 }, (_, i) => `key-${i}`));
+const strSet100 = new Set(Array.from({ length: 100 }, (_, i) => `key-${i}`));
+
+const objSet10 = new Set(Array.from({ length: 10 }, (_, i) => ({ id: i })));
+const objSet100 = new Set(Array.from({ length: 100 }, (_, i) => ({ id: i })));
+
+bench("[...set] - integers (10)", () => [...intSet10]);
+bench("[...set] - integers (100)", () => [...intSet100]);
+bench("[...set] - strings (10)", () => [...strSet10]);
+bench("[...set] - strings (100)", () => [...strSet100]);
+bench("[...set] - objects (10)", () => [...objSet10]);
+bench("[...set] - objects (100)", () => [...objSet100]);
+
+await run();