Compile common stdlib tests against common stdlib

Declare platform-specific test utilities as expect.

js/js.libraries/test/core/testUtils.kt

@@ -14,11 +14,14 @@
  * limitations under the License.
  */
 
-package kotlin.test
+package test
+
+import kotlin.test.*
 
 public fun assertTypeEquals(expected: Any?, actual: Any?) {
     assertEquals(expected?.let { it::class.js }, actual?.let { it::class.js })
 }
 
+@Suppress("NOTHING_TO_INLINE")
 internal inline fun String.removeLeadingPlusOnJava6(): String = this
 internal fun doubleTotalOrderEquals(a: Double?, b: Double?) = a == b || (a != a && b != b)