Deprecate join (use joinToString instead)

#KT-6909

libraries/stdlib/test/collections/CollectionTest.kt

@@ -14,13 +14,13 @@ class CollectionTest {
         assertEquals("{foo-bar}", buffer.toString())
     }
 
-    @test fun join() {
+    @test fun joinToString() {
         val data = listOf("foo", "bar")
-        val text = data.join("-", "<", ">")
+        val text = data.joinToString("-", "<", ">")
         assertEquals("<foo-bar>", text)
 
         val big = listOf("a", "b", "c", "d", "e", "f")
-        val text2 = big.join(limit = 3, truncated = "*")
+        val text2 = big.joinToString(limit = 3, truncated = "*")
         assertEquals("a, b, c, *", text2)
     }