KonanTest: infrostructure enhancements.

- test status in enum.
- fails are bit different from errors.

it takes reports generated in output directory and sum statistics and publish
result on slack.

backend.native/tests/testUtils.kt

@@ -0,0 +1,5 @@
+package kotlin.test
+
+class TestFailedException(val msg:String):RuntimeException(msg)
+
+fun <T> assertEquals(a:T, b:T, msg:String) { if (a != b) throw TestFailedException(msg) }