Fix NetworkConfig default constructor issue

Fix RealtimeDatabase issue #206

Fix the undetectable timeout issue #203

Apply ESP32 Client.h Arduino API breaking fix only for ESP32 Arduino …

…Core v3.1.0

Fix ESP32 Core v3.x.x warning and some improvement

Fix chunked data issue #201

Fix incomplete chunked data issue #200

Update PPP and GSM examples

Fix PPP compilation error in ESP32 Core v3.x.x

Add support PPP network in ESP32 Core v3.x.x