Baseline for the tests is similar to the TDBStore.
Differing from TDBStore moduletests, FileSystemStore doesn't include
tests for reserved data or corrupting the blockdevice, as it corrupts
the filesystem also.
GoogleTest allows you to check whether certain function throws errors.
For example:
ASSERT_ANY_THROW(mbed::HeapBlockDevice one(3050, 100));
or
ASSERT_NO_THROW(bd.init());
As MBED_ERROR is now only function that can throw errors, there is
no need to check the type of thrown object.
For UTs mbed_assert_internal should not be declared as MBED_NORETURN
as UT stub for mbed_assert_internal only prints out the assert trace
and returns back to original code.
-Added the mock class function to mock mbed_assert_internal
-Added the unit test case to test start,kick,stop
-Modified the interface api name from is_alive to process
-added the unit test cases for process