tests: Copy stdlib tests from Kotlin/JVM

This patch copies Kotlin/JVM stdlib tests (libraries/stdlib/test)
excepting ones with explicit java dependencies. It also transforms
the tests to use them as box-tests.

backend.native/tests/external/stdlib/text/StringTest/endsWithString.kt

@@ -0,0 +1,14 @@
+import kotlin.test.*
+
+
+
+fun box() {
+    assertTrue("abcd".endsWith("d"))
+    assertTrue("abcd".endsWith("abcd"))
+    assertFalse("abcd".endsWith("b"))
+    assertFalse("strö".endsWith("RÖ", ignoreCase = false))
+    assertTrue("strö".endsWith("RÖ", ignoreCase = true))
+    assertFalse("".endsWith("a"))
+    assertTrue("some".endsWith(""))
+    assertTrue("".endsWith(""))
+}