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/matchSequence.kt

@@ -0,0 +1,18 @@
+import kotlin.text.*
+
+import kotlin.test.*
+
+
+fun box() {
+    val input = "123 456 789"
+    val pattern = "\\d+".toRegex()
+
+    val matches = pattern.findAll(input)
+    val values = matches.map { it.value }
+    val expected = listOf("123", "456", "789")
+    assertEquals(expected, values.toList())
+    assertEquals(expected, values.toList(), "running match sequence second time")
+    assertEquals(expected.drop(1), pattern.findAll(input, startIndex = 3).map { it.value }.toList())
+
+    assertEquals(listOf(0..2, 4..6, 8..10), matches.map { it.range }.toList())
+}