Make ETHERNET configuration the default if DEVICE_EMAC is present,
instead of if FEATURE_LWIP is present.
This limits it to targets which have been ported to the new EMAC API.
Add LWIP feature to JSON config, as in principle the targets shouldn't
be adding it themselves. Opens scope to having Nanostack-based tests.
Disable tests for the Realtek and Wifi drivers that aren't ported yet.
Not all devices have enough heap to fit a simulated heap block device,
however using a simulated heap block device is preferred if available
(reduced flash wear, faster testing).
Added MBED_TEST_SIM_BLOCKDEVICE for tests that only need a simulated
block device (wear_leveling + resilience), and added support for targets
that are known to have enough heap.
Veijo Pesonen
Kevin Bracey
Mika Leppänen
Christopher Haster
Sarah Marsh