Rename filterNull to filterNotNull such as Kotlin Std Collections (#259)

Author: nomisRev

arrow-libs/fx/arrow-fx-coroutines/src/main/kotlin/arrow/fx/coroutines/stream/Stream.kt

@@ -2153,14 +2153,14 @@ fun <O> Stream<O>.repartition(S: Semigroup<O>, f: (O) -> Chunk<O>): Stream<O> =
  * //sampleStart
  * suspend fun main(): Unit =
  *   Stream(1, 2, null, 3, None)
- *     .filterNull()
+ *     .filterNotNull()
  *     .compile()
  *     .toList()
  *     .let(::println) //[1, 2, 3]
  * //sampleEnd
  * ```
  */
-fun <O : Any> Stream<O?>.filterNull(): Stream<O> =
+fun <O : Any> Stream<O?>.filterNotNull(): Stream<O> =
   mapFilter { it }
 
 /**

arrow-libs/fx/arrow-fx-coroutines/src/test/kotlin/arrow/fx/coroutines/stream/StreamTest.kt

@@ -235,6 +235,14 @@ class StreamTest : StreamSpec(spec = {
     }
   }
 
+  "filterNotNull" {
+    checkAll(Arb.stream(Arb.int().orNull())) { s ->
+      s.filterNotNull()
+        .compile()
+        .toList() shouldBe s.compile().toList().filterNotNull()
+    }
+  }
+
   "append" {
     checkAll(Arb.stream(Arb.int()), Arb.stream(Arb.int())) { s1, s2 ->
       s1.append { s2 }.compile().toList() shouldBe s1.compile().toList() + s2.compile().toList()