"malloc" test is used a simple thread that executes only malloc and free, but it seems that there is a difference in the stack used between Cortex-A and Cortex-M.
As a result of check, in Cortex-A, program aborts because of the lack of stack when THREAD_STACK_SIZE is 256, workes properly when THREAD_STACK_SIZE is 512 at least. Since it seems that the definition processing of "DEFAULT_STACK_SIZE" was gone from Mbed OS by updating CMSIS5/RTX5, I setted 512 directly for Cortex-A.
Reduce RAM consumption so all tests can still be built when using
CMSIS/RTX5. Also reduce clutter by removing the per target stack size
defines in the tests.