Description

Support for WPA3 and hidden SSIDs (note that correct channel plan e.g. US needs to be set for 5GHz hidden SSID support to work, otherwise 5GHz scans are passive).

Steps to Test

1. Configure WPA3 credentials over Serial in listening mode and attempt to connect (need to select '6' for WPA3, won't be prompted as an option)
2. Configure credentials with hidden SSID with a test app and attempt to connect

    WiFiCredentials cred;
    cred.setSsid("Particle");
    cred.setPassword("Particle");
    cred.setCipher(WLAN_CIPHER_AES);
    cred.setSecurity(spark::SecurityType::WPA2);
    cred.setHidden(true);
    WiFi.setCredentials(cred);

Problems

CLI uses hardcoded serial prompts as triggers (https://github.com/particle-iot/particle-cli/blob/master/src/cmd/serial.js#L1003), adding WPA3 option there breaks older CLI.

Should we migrate to using USB requests instead?

Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)