unity: separate common and IDF specific functionality

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.

components/esp32/include/esp_clk.h

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #pragma once
+#include <stdint.h>
 
 /**
  * @file esp_clk.h