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/StringNumberConversionTest/byteToStringWithRadix.kt

@@ -0,0 +1,13 @@
+import kotlin.test.*
+
+
+
+fun box() {
+    assertEquals("7a", 0x7a.toByte().toString(16))
+    assertEquals("-80", Byte.MIN_VALUE.toString(radix = 16))
+    assertEquals("3v", Byte.MAX_VALUE.toString(radix = 32))
+    assertEquals("-40", Byte.MIN_VALUE.toString(radix = 32))
+
+    assertFailsWith<IllegalArgumentException>("Expected to fail with radix 37") { 37.toByte().toString(radix = 37) }
+    assertFailsWith<IllegalArgumentException>("Expected to fail with radix 1") { 1.toByte().toString(radix = 1) }
+}