Enable shared stack watchpoint for overflow detection
Enable unit tests:
* "test printf using shared buffer stack" for C3
* "Test vTaskDelayUntil" for S2
* "UART can do poll()" for C3
The riscv vectors.S in riscv component contains the trap vector, which is responsible to
defer interrupts and examine if a task context switch is needed, this change cleans up
this code by hiding all freertos details behind on two functions rtos_it_enter/exit and
their implementations are placed in freertos riscv port files.
