[ HipHop Debugger ] `dict[0 => NAN]` equals itself in the debugger, but not cli or server mode

**Describe the bug**
Comparing the value `dict[0 => NAN]` to itself is equal in the HipHop debugger `hhvm --no-config -a`. When running are script from the cli or in a webserver, these values are not equal.

**Standalone code, or other way to reproduce the problem**

```HACK
<<__EntryPoint>>
function main(): void {
echo (dict[0 => NAN] === dict[0 => NAN] ? 'equal' : 'not equal')."\n";
}
```

Steps to reproduce the behavior:
1. Run the above code from the cli using `hhvm --no-config file.hack`
2. Run the above code in web server mode using `hhvm --no-config -m server -p 8080` and visit localhost:8080/file.hack
3. Observe `not equal` being printed in both cases.
4. Start the HipHop debugger using `hhvm --no-config -a`.
5. Paste the following statement `echo (dict[0 => NAN] === dict[0 => NAN] ? 'equal' : 'not equal')."\n";`.
6. Observe `equal` being printed.

**Expected behavior**

The behavior of this comparison should not differ between debugger and script mode. From my understanding, they should compare equal.

See: https://github.com/facebook/hhvm/blob/master/hphp/test/slow/comparisons/nan_array_id_test.php and https://github.com/facebook/hhvm/blob/master/hphp/test/slow/comparisons/nan_array_id_test.php.expect

My understanding could be wrong here, so please verify what the proper behavior should be with someone in the know first.

**Actual behavior**

Output differs between the debugger and cli / server mode.

**Environment**
- Operating system
> Ubuntu 18.04
- Installation method
> apt-get with dl.hhvm.com repository
- HHVM Version
```
HipHop VM 4.169.0 (rel) (non-lowptr)
Compiler: 1663640616_852546864
Repo schema: ce4145c518e16986e860178941c05dc9f11eab61
```

**Additional context**
N/A

Start by running the Hack reproduction in CLI mode and with `hhvm --no-config -a`, then read `hphp/test/slow/comparisons/nan_array_id_test.php` and its `.expect` file. Trace how the debugger evaluates the comparison versus script mode, and verify the expected behavior with a relevant maintainer. Done means the modes agree and the comparison test documents the result.

Written by the indexing model from the issue text.