Implement WiFiClientSecure (for TLS MQTT)

[vidplace7]

WiFiClientSecure should be implemented in portduino, so that MQTT with TLS can be supported 🙏

https://github.com/meshtastic/firmware/blob/3787cf78034fad1534a954c7b654dace05cbf4e4/src/mqtt/MQTT.h#L82-L85

[cocus]

I have implemented the WiFiClientSecure using ESP32's implementation, which uses mbedtls under the hood. I'm currently testing it locally, but looks good. Not sure about adding the mbedtls dependency on the platform-native repo, due to the fact that WiFiClientSecure.cpp and ssl_client.cpp both uses mbedtls (and both are files of framework-portduino).

It seems it has taken my changes, and it might be working, but I'm having issues setting up the client at all. The webserver doesn't work, and using client.meshtastic.org I can't add my own one (i.e. the meshtasticd running locally, with the module set to sim). Any insights?

EDIT: I've got the webserver going, I forgot to install additional packages. It seems that the WiFiClientSecure is being used, but I can't tell if it works or not, because I was never able to connect to my local mqtts server, not even with an esp32 device. I know it's skill issue, but oh well.

EDIT2: I've got this output, but as I stated, I don't know if this is working or not:

INFO  | 20:43:55 0 [mqtt] Use TLS-encrypted session
INFO  | 20:43:55 0 [mqtt] Connecting directly to MQTT server mesharg.innova.ar, port: 8883, username: cocus, password: <redacted>
Starting socket (domain 2)
Seeding the random number generator
Setting up the SSL/TLS structure...
WARNING: Skipping SSL Verification. INSECURE!
Setting hostname for TLS session...
Performing the SSL/TLS handshake...
Verifying peer X.509 certificate...
Certificate verified.
INFO  | 20:43:55 0 [mqtt] MQTT connected
INFO  | 20:43:55 0 [mqtt] Subscribe to msh/AR/2/e/LongFast/+
INFO  | 20:43:55 0 [mqtt] Subscribe to msh/AR/2/e/PKI/+

(note those debug strings without the "meshtastic logging color" come from the WiFiClientSecure.cpp or ssl_client.cpp)
and then:

DEBUG | 20:44:25 30 [NodeInfo] Use AES128 key!
DEBUG | 20:44:25 30 [NodeInfo] MQTT onSend - Publish 
DEBUG | 20:44:25 30 [NodeInfo] encrypted message
DEBUG | 20:44:25 30 [NodeInfo] MQTT Publish msh/AR/2/e/LongFast/!36ad4ec0, 143 bytes
DEBUG | 20:44:25 30 [NodeInfo] enqueuing for send (id=0x9894ec59 fr=0x36ad4ec0 to=0xffffffff, transport = 0, WantAck=0, HopLim=3 Ch=0x8 encrypted len=102 rxtime=1771706665 hopStart=3 relay=0xc0 priority=10)

EDIT3: Seems like the MQTT server that was used in argentina is down. I made my own one, and I can see the messages going through (although they're encrypted). I'd say these changes work. I'm really sorry that I didn't use openssl, but the code was easier to just "take" from the mbedtls version of the ESP32. I tried piping this code I have to copilot to port it to openssl, but it didn't work. I'll wait for any feedback here, but I plan to open a PR to both meshtastic firmware and this repo.