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/RegexTest/split.kt

@@ -0,0 +1,16 @@
+import kotlin.text.*
+
+import kotlin.test.*
+
+
+fun box() {
+    val input = """
+     some  ${"\t"}  word
+     split
+    """.trim()
+
+    assertEquals(listOf("some", "word", "split"), "\\s+".toRegex().split(input))
+
+    assertEquals(listOf("name", "value=5"), "=".toRegex().split("name=value=5", limit = 2))
+
+}