[nat64] change BORDER_ROUTING_NAT64 to NAT64_BORDER_ROUTING (#8047)

We decided to rename BORDER_ROUTING_NAT64 to NAT64_BORDER_ROUTING so
the flag won't be confusing since we have NAT64_TRANSLATOR which does
not depends on the border routing manager.

include/openthread/border_routing.h

@@ -216,7 +216,7 @@ otError otBorderRoutingGetOnLinkPrefix(otInstance *aInstance, otIp6Prefix *aPref
  *
  * NAT64 Prefix might not be advertised in the Thread network.
  *
- * `OPENTHREAD_CONFIG_BORDER_ROUTING_NAT64_ENABLE` must be enabled.
+ * `OPENTHREAD_CONFIG_NAT64_BORDER_ROUTING_ENABLE` must be enabled.
  *
  * @param[in]   aInstance   A pointer to an OpenThread instance.
  * @param[out]  aPrefix     A pointer to where the prefix will be output to.

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (239)
+#define OPENTHREAD_API_VERSION (240)
 
 /**
  * @addtogroup api-instance

include/openthread/nat64.h

@@ -46,7 +46,7 @@ extern "C" {
  * @addtogroup api-nat64
  *
  * @brief This module includes functions and structs for the NAT64 function on the border router. These functions are
- * only available when `OPENTHREAD_CONFIG_BORDER_ROUTING_NAT64_ENABLE` is enabled.
+ * only available when `OPENTHREAD_CONFIG_NAT64_BORDER_ROUTING_ENABLE` is enabled.
  *
  * @{
  *