Defaulted to HeapBlockDevice. Unfortunately this does mean that
by default almost none of the tests are actually capable of running
unless the dut has >512KB or RAM.
Add tests for filesystem resilience and wear leveling. These tests
take shared filesystem code and simulate different scenarios while
this code is running. Information on the new tests can be found below.
mbed-littlefs-tests-filesystem_recovery-resilience:
Tests that after every block device operation the filesystem is in a
well defined state.
mbed-littlefs-tests-filesystem_recovery-wear_leveling:
Tests that the littlefs correctly handles when flash is exhausted by
using a simulated block device until there are no free good blocks.
Note - This patch also adds several new block devices for testing.
These will eventually be moved into mbed-os.