RainMaker library: Minor changes (#5092)

- Use Serial.print instead of log_i for QR code helper information,
  so that it is always printed by default.
- Expose the RainMaker factory reset and wifi reset APIs.
- Simplify example to have only a Switch device. Create another example for custom device.
- Enable push button based Factory reset and Wi-Fi reset.
- Added support for the TimeZone service.
- Moved API doc to RainMaker library's top level README.
- Other minor doc changes.

libraries/RainMaker/examples/RMakerSwitch/README.md

@@ -0,0 +1,27 @@
+# ESP RainMaker Switch
+
+This example demonstrates how to build a switch device to be used with ESP RainMaker.
+
+## What to expect in this example?
+
+- This example sketch uses the on board Boot button and GPIO16 to demonstrate an ESP RainMaker switch device.
+- After compiling and flashing the example, add your device using the [ESP RainMaker phone apps](https://rainmaker.espressif.com/docs/quick-links.html#phone-apps) by scanning the QR code.
+- Toggling the state from the phone app will toggle the switch state (GPIO16).
+- Pressing the Boot button will toggle the switch state (GPIO16) and the same will reflect on the phone app.
+
+### Output
+
+```
+[    63][I][RMaker.cpp:13] event_handler(): RainMaker Initialised.
+[    69][I][WiFiProv.cpp:158] beginProvision(): Already Provisioned
+[    69][I][WiFiProv.cpp:162] beginProvision(): Attempting connect to AP: Viking007_2GEXT
+
+Toggle State to false.
+[  8182][I][RMakerDevice.cpp:162] updateAndReportParam(): Device : Switch, Param Name : Power, Val : false
+Toggle State to true.
+[  9835][I][RMakerDevice.cpp:162] updateAndReportParam(): Device : Switch, Param Name : Power, Val : true
+Received value = false for Switch - Power
+Received value = true for Switch - Power
+Toggle State to false.
+[ 29937][I][RMakerDevice.cpp:162] updateAndReportParam(): Device : Switch, Param Name : Power, Val : false
+```