[openthread] Update message buffer settings, fix join beacon version

The default settings for message buffers are geared more toward
microcontroller than full hosts. This CL increases the memory reserved
for memory buffers, as well as increases the maximum number of outstanding memory buffers. This should help improve throughput
consistency.

This CL also removes setting OPENTHREAD_CONFIG_MAC_JOIN_BEACON_VERSION
to `1`, which was only needed for commissioning legacy devices which
are no longer supported.

Bug: 105869
Change-Id: I6d035645c6a9fdeab92658136fcba2d564498dcd
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/openthread/+/708465
Reviewed-by: Robert Quattlebaum <rquattle@google.com>
(cherry picked from commit 5d72600fca217a8cba2e591beca52681a08c32c2)
diff --git a/include/openthread-config-fuchsia.h b/include/openthread-config-fuchsia.h
index a21ebaf..d9dd290 100644
--- a/include/openthread-config-fuchsia.h
+++ b/include/openthread-config-fuchsia.h
@@ -139,14 +139,6 @@
 #define OPENTHREAD_CONFIG_LOG_LEVEL OT_LOG_LEVEL_NOTE
 
 /**
- * @def OPENTHREAD_CONFIG_MAC_JOIN_BEACON_VERSION
- *
- * The Beacon version to use when the beacon join flag is set.
- *
- */
-#define OPENTHREAD_CONFIG_MAC_JOIN_BEACON_VERSION 1
-
-/**
  * @def OPENTHREAD_CONFIG_IP6_MAX_EXT_MCAST_ADDRS
  *
  * The maximum number of supported IPv6 multicast addresses allows to be externally added.
@@ -170,7 +162,10 @@
  * Rx frame buffer in openthread
  *
  */
-#define OPENTHREAD_CONFIG_PLATFORM_RADIO_SPINEL_RX_FRAME_BUFFER_SIZE 24576
+#define OPENTHREAD_CONFIG_PLATFORM_RADIO_SPINEL_RX_FRAME_BUFFER_SIZE 65535
+
+// The number of outstanding message buffers allowed to be allocated.
+#define OPENTHREAD_CONFIG_NUM_MESSAGE_BUFFERS 512
 
 /**
  * @def OPENTHREAD_CONFIG_MLE_LINK_METRICS_SUBJECT_ENABLE