[SYCL][Docs] Move sycl_ext_oneapi_enqueue_functions to experimental (#14017)

#13512 implemented the
sycl_ext_oneapi_enqueue_functions extension. Following this, the
corresponding extension document is moved to experimental and the
feature test macro is defined.

---------

Signed-off-by: Larsen, Steffen <[email protected]>

Author: steffenlarsen

sycl/doc/extensions/proposed/sycl_ext_oneapi_enqueue_functions.asciidoc renamed to sycl/doc/extensions/experimental/sycl_ext_oneapi_enqueue_functions.asciidoc

@@ -44,11 +44,12 @@ SYCL specification refer to that revision.
 
 == Status
 
-This is a proposed extension specification, intended to gather community
-feedback.  Interfaces defined in this specification may not be implemented yet
-or may be in a preliminary state.  The specification itself may also change in
-incompatible ways before it is finalized.  *Shipping software products should
-not rely on APIs defined in this specification.*
+This is an experimental extension specification, intended to provide early
+access to features and gather community feedback.  Interfaces defined in this
+specification are implemented in {dpcpp}, but they are not finalized and may
+change incompatibly in future versions of {dpcpp} without prior notice.
+*Shipping software products should not rely on APIs defined in this
+specification.*
 
 
 == Overview
@@ -79,7 +80,7 @@ This extension makes SYCL simpler and easier to document. It is also expected
 to improve the performance of many SYCL applications, where `event` objects are
 not required to describe application behavior.
 
-All functions proposed in this extension accept as their first argument an
+All functions in this extension accept as their first argument an
 object that represents where a command should be submitted, allowing the new
 functions to be used either at command-group scope or as a replacement for
 existing queue shortcuts. A future version of this extension may adjust this
@@ -89,7 +90,7 @@ by accepting a scheduler and returning a sender).
 
 === Usage example
 
-The example below demonstrates that the syntax proposed here requires only
+The example below demonstrates that the syntax here requires only
 minor changes to existing applications, while retaining their structure.
 
 
@@ -117,7 +118,7 @@ sycl::free(output, q);
 ----
 
 
-==== Proposed syntax
+==== Syntax
 
 [source,c++]
 ----

sycl/source/feature_test.hpp.in

@@ -107,6 +107,7 @@ inline namespace _V1 {
 #define SYCL_EXT_ONEAPI_FORWARD_PROGRESS 1
 #define SYCL_EXT_ONEAPI_FREE_FUNCTION_KERNELS 1
 #define SYCL_EXT_ONEAPI_PROD 1
+#define SYCL_EXT_ONEAPI_ENQUEUE_FUNCTIONS 1
 
 #ifndef __has_include
 #define __has_include(x) 0