Add experimental fromNullable for explicit nulls

Author: noti0na1

library/src/scala/runtime/stdLibPatches/Predef.scala

@@ -62,4 +62,8 @@ object Predef:
      *  `eq` or `ne` methods, only `==` and `!=` inherited from `Any`. */
     inline def ne(inline y: AnyRef | Null): Boolean =
       !(x eq y)
+
+  extension (inline opt: Option.type)
+    @experimental
+    inline def fromNullable[T](t: T | Null): Option[T] = Option(t).asInstanceOf
 end Predef