portBASE_TYPE is an internal macro defined by the porting layer. This commit
changes all references to BaseType_t which is the official type exposed by
FreeRTOS.
This commit refactors port_common.c so that it only contains implementation of
FreeRTOS port functions that are common to all FreeRTOS ports (i.e., on all
architectures and on all FreeRTOS implementations).
* Added port layer from the FreeRTOS POSIX port, added
additional port code for ESP-IDF.
* Created another hello world example using that POSIX
port in tools/test_apps.
* Removed old linux app
