Support hidden SSIDs when connecting via Captive Portal

**Describe the problem you have/What new integration you would like**
I can't connect to a hidden SSID when configuring WiFi connection via Captive Portal.

**Please describe your use case for this integration and alternatives you've tried:**
I want to flash multiple devices with AP + Captive Portal only (no default WiFi connection), so that when they are plugged in they can be configured to connect to a hidden WiFi network.

**Additional context**
At the moment it does not seem to work:

```
[20:21:21][D][wifi:365]: Starting scan...
[20:21:27][D][wifi:380]: Found networks:
[20:21:27][D][wifi:430]: - '' (E3:62:DA:1C:02:DA) ▂▄▆█
[20:21:27][D][wifi:430]: - 'SPARK-ABCDE' (58:BA:E1:82:5D:78) ▂▄▆█
[20:21:27][D][wifi:430]: - 'vodafone123456' (11:12:71:B6:A6:51) ▂▄▆█
[20:21:27][W][wifi:435]: No matching network found!
```

No files or tests are named. Start by tracing the Captive Portal WiFi connection flow and the scan path that reports “No matching network found!” for the empty SSID. Done means devices configured through the portal can connect to a hidden WiFi network in the described AP-only setup.

Written by the indexing model from the issue text.