Matter POC for remote Relay

[s-hadinger]

Description:

Matter: Proof of Concept for a remote Tasmota relay. This allows to use an ESP32 based Matter device to control a relay from another ESP8266 based Tasmota device, through pure HTTP communication.

This is just a POC without bridged support, which means that adding a remote relay requires to remove the Matter device from the controller and pair it again. In the future, using "bridged" mode should make it possible to dynamically add endpoints.

Parameter: <relay_index>,<url>:

• <relay_index> contains the index of the relay (0 based, so substract 1 to the actual Relay GPIO number)
• <url> contains either the IP address (ex: 192.168.1.100) or a full HTTP domain (ex: http://192.168.1.100/)

Example:

Also includes a refactoring of the scheduler for the updates of shadow attributes.

Current limitations:

• a future optimization will be needed in the same remote Tasmota device is used in several endpoints (like multiple relays) so as to group HTTP requests and reduce Wifi traffic
• add exponential backoff if a device is not reachable (timeout)
• HTTP client timeout is 1000 ms, it needs to be reduced but it does not seem possible with the current library
• ideally implement asynchronous web client (not sure it's easy enough)

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.8
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass