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/replace.kt

@@ -0,0 +1,13 @@
+import kotlin.text.*
+
+import kotlin.test.*
+
+
+fun box() {
+    val input = "123-456"
+    val pattern = "(\\d+)".toRegex()
+    assertEquals("(123)-(456)", pattern.replace(input, "($1)"))
+
+    assertEquals("$&-$&", pattern.replace(input, Regex.escapeReplacement("$&")))
+    assertEquals("X-456", pattern.replaceFirst(input, "X"))
+}