Make default SerialBT FIFO 1K (#3032)

BT SPP doesn't have backoff and we can receive long
messages.  If there's not enough memory to store them
then they will be truncated.

Increase the default space to 1K to help avoid this issue.

Author: earlephilhower

libraries/SerialBT/src/SerialBT.h

@@ -79,7 +79,7 @@ class SerialBT_ : public HardwareSerial {
     // Lockless, IRQ-handled circular queue
     uint32_t _writer;
     uint32_t _reader;
-    size_t   _fifoSize = 32;
+    size_t   _fifoSize = 1024;
     uint8_t *_queue;
 
     const int RFCOMM_SERVER_CHANNEL = 1;