[tuya] Batch UART reads to reduce per-loop overhead

Replace byte-at-a-time read_byte() calls with batched read_array()
in loop(). Each read_byte() internally chains through
read_array(data, 1) -> check_read_timeout_(1) -> available(),
resulting in ~3 UART driver calls per byte. Batching into a 64-byte
stack buffer reduces this to ~3 calls per loop iteration regardless
of how many bytes are available.

esphome/components/tuya/tuya.cpp

@@ -31,10 +31,21 @@ void Tuya::setup() {
 }
 
 void Tuya::loop() {
-  while (this->available()) {
-    uint8_t c;
-    this->read_byte(&c);
-    this->handle_char_(c);
+  int avail = this->available();
+  if (avail > 0) {
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read)) {
+        break;
+      }
+      avail -= to_read;
+
+      for (size_t i = 0; i < to_read; i++) {
+        this->handle_char_(buf[i]);
+      }
+    }
   }
   process_command_queue_();
 }