Add RTL_433 device whitelist support

[waiet]

Summary

This PR adds an optional whitelist for the RTL_433 gateway.

When enabled, only RTL_433 devices whose generated device identifier is present in the whitelist are published to MQTT. Non-whitelisted RTL_433 messages are ignored. The whitelist is persisted in preferences and can be managed from the WebUI RF configuration page or through MQTT SYS commands.

The Home Assistant MQTT discovery payload also exposes a gateway switch to enable or disable the RTL_433 whitelist.

Details

• Adds persistent RTL_433 whitelist configuration
• Uses the RTL_433 device identifier format: type/model/subtype/channel/id
• Tracks seen RTL_433 devices during runtime so they can be selected from the WebUI
• Filters MQTT publishing and RTL_433 discovery when the whitelist is enabled
• Adds RTL_433: Whitelist switch to Home Assistant discovery
• Publishes whitelist state in the SYS state topic

Testing

Built successfully with PlatformIO:

• esp32dev-rtl_433
• lilygo-rtl_433

Also tested on an ESP32 + CC1101 setup receiving 433 MHz weather sensor data.

[Odyno]

I hope you're luckier :) I made a Merge Request #2252 to provide this functionality (if I understand correctly) globally as an evolution of another one I made even earlier for the RF gateway only... but unfortunately the bot passed and shut down before @1technophile did the necessary testing... if you care keep the thread alive otherwise it will happen like my MR