[Issue #1187] Add nan_to_num function initial attempt (#1247)

* initial attempt, working with wrong types

* not compiling; mx.float16 and mx.bfloat16 tests added

* fix nan to num

* nit

---------

Co-authored-by: Awni Hannun <awni@apple.com>

mlx/ops.h

@@ -406,6 +406,14 @@ array where(
     const array& y,
     StreamOrDevice s = {});
 
+/** Replace NaN and infinities with finite numbers. */
+array nan_to_num(
+    const array& a,
+    float nan = 0.0f,
+    const std::optional<float>& posinf = std::nullopt,
+    const std::optional<float>& neginf = std::nullopt,
+    StreamOrDevice s = {});
+
 /** True if all elements in the array are true (or non-zero). **/
 array all(const array& a, bool keepdims, StreamOrDevice s = {});
 inline array all(const array& a, StreamOrDevice s = {}) {