feat(url): implement URLPattern API (#25168)

## Summary

Implements the [URLPattern Web
API](https://developer.mozilla.org/en-US/docs/Web/API/URLPattern) based
on WebKit's implementation. URLPattern provides declarative pattern
matching for URLs, similar to how regular expressions work for strings.

### Features

- **Constructor**: Create patterns from strings or `URLPatternInit`
dictionaries
- **`test()`**: Check if a URL matches the pattern (returns boolean)
- **`exec()`**: Extract matched groups from a URL (returns
`URLPatternResult` or null)
- **Pattern properties**: `protocol`, `username`, `password`,
`hostname`, `port`, `pathname`, `search`, `hash`
- **`hasRegExpGroups`**: Detect if the pattern uses custom regular
expressions

### Example Usage

```js
// Match URLs with a user ID parameter
const pattern = new URLPattern({ pathname: '/users/:id' });

pattern.test('https://example.com/users/123'); // true
pattern.test('https://example.com/posts/456'); // false

const result = pattern.exec('https://example.com/users/123');
console.log(result.pathname.groups.id); // "123"

// Wildcard matching
const filesPattern = new URLPattern({ pathname: '/files/*' });
const match = filesPattern.exec('https://example.com/files/image.png');
console.log(match.pathname.groups[0]); // "image.png"
```

## Implementation Notes

- Adapted from WebKit's URLPattern implementation
- Modified JS bindings to work with Bun's infrastructure (simpler
`convertDictionary` patterns, WTF::Variant handling)
- Added IsoSubspaces for proper GC integration

## Test Plan

- [x] 408 tests from Web Platform Tests pass
- [x] Tests fail with system Bun (URLPattern not defined), pass with
debug build
- [x] Manual testing of basic functionality

Fixes https://github.com/oven-sh/bun/issues/2286

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

bench/snippets/urlpattern.js

@@ -0,0 +1,48 @@
+import { bench, group, run } from "../runner.mjs";
+
+const patterns = [
+  { name: "string pattern", input: "https://(sub.)?example(.com/)foo" },
+  { name: "hostname IDN", input: { hostname: "xn--caf-dma.com" } },
+  {
+    name: "pathname + search + hash + baseURL",
+    input: {
+      pathname: "/foo",
+      search: "bar",
+      hash: "baz",
+      baseURL: "https://example.com:8080",
+    },
+  },
+  { name: "pathname with regex", input: { pathname: "/([[a-z]--a])" } },
+  { name: "named groups", input: { pathname: "/users/:id/posts/:postId" } },
+  { name: "wildcard", input: { pathname: "/files/*" } },
+];
+
+const testURL = "https://sub.example.com/foo";
+
+group("URLPattern parse (constructor)", () => {
+  for (const { name, input } of patterns) {
+    bench(name, () => {
+      return new URLPattern(input);
+    });
+  }
+});
+
+group("URLPattern.test()", () => {
+  for (const { name, input } of patterns) {
+    const pattern = new URLPattern(input);
+    bench(name, () => {
+      return pattern.test(testURL);
+    });
+  }
+});
+
+group("URLPattern.exec()", () => {
+  for (const { name, input } of patterns) {
+    const pattern = new URLPattern(input);
+    bench(name, () => {
+      return pattern.exec(testURL);
+    });
+  }
+});
+
+await run();