mbed.h was added in test, via greentea and utest header files. 'mbed.h' is removed
from header files and required header file and namespace is added to CPP/C files
1. RTOS is needed only for Stack stats
Move+Add all required header files for RTOS into MBED_STACK_STATS_ENABLED
define. Also added 'using namespace'
2. Add heap stats only when MBED_HEAP_STATS_ENABLED
Move the metrics mutex into the ifdef MBED_STACK_STATS_ENABLED since
it is not used ouside of it. This fixes the warning:
[Warning] greentea_metrics.cpp@37,28: 'mutex' defined but not used [-Wunused-variable]
Update greentea to report thread information when a thread exits or
is terminated and when testing completes. Also move metrics into
a dedicated greentea file.