New unity component can be used for testing other applications.
Upstream version of Unity is included as a submodule.
Utilities specific to ESP-IDF unit tests (partitions, leak checking
setup/teardown functions, etc) are kept only in unit-test-app.
Kconfig options are added to allow disabling certain Unity features.
spi test: Prime the flash cache before each test to minimise flash cache misses.
VFS performance test: Increase the number of runs to minimise influence of an isolated bad run.
