[9.x] Adds support for PHP's BackedEnum to be "rendered" on blade views.

[nunomaduro]

This pull request is a very simple change that allows PHP's BackedEnum to be "rendered" on blade views.

enum UserRoles: string
{
    case ADMIN = 'Admin';
}

// routes/web.php
Route::get('/', function () {
    return view('dashboard', ['role' => UserRoles:: ADMIN]);
});

// dashboard.blade.php
Hello, {{ $role }}.

// ❌ Before: TypeError: htmlspecialchars(): Argument #1 ($string) must be of type string
// ✅ After: Hello, Admin.

Fixes #44431.