Add cellular library submodule path and demo (#695)

* [Cellular] Add cellulr lib submodule and demo app

* [Cellular] Fix memory violation in transport layer and add using LoggingPrintf

* Update FreeRTOS Cellular Interface

* Change the mbedtls usage in FreeRTOS-Plus

* [Cellular] Fix missing spell

* [Cellular] Add manifest.yml

* Fix missing spell

* Update manifest.yml

* [Cellular] Add integration test

* Modify the demo log level to LOG_INFO

* Update cellular interface

* The modification of the folder structure for cellular library

* Rename the naming of demo

* Adjust the location of using_mbedtls and socket_wrapper

* Adjust project setting for relocating using_mbedtls and socket_wrapper

* Turn off PSM mode

* Add start marker for CI validation.

* The modification for mbedtls platform send/recv function for cellular

* Change the project file due to the changes of mbedtls platform send/recv function for cellular

* Fix missing newline and remove unused file

* Add missing configuration.

* Make cellular and freertos tcp plus use the same transport implementation

* Add comment for the macro MBEDTLS_SSL_SEND and MBEDTLS_SSL_RECV

* Make changes from the github comment.

manifest.yml

@@ -122,4 +122,11 @@ dependencies:
       url: "https://github.com/FreeRTOS/FreeRTOS-Partner-Supported-Demos"
       path: "FreeRTOS/Demo/ThirdParty/Partner-Supported-Demos"
 
+  - name: "FreeRTOS-Cellular-Interface"
+    version: "d35316b"
+    repository:
+      type: "git"
+      url: "https://github.com/FreeRTOS/FreeRTOS-Cellular-Interface.git"
+      path: "FreeRTOS-Plus/Source/FreeRTOS-Cellular-Interface"
+
 license: "MIT"