[usb_uart] Add FTDI FT23XX USB UART driver (#14587)

Co-authored-by: Oliver Kleinecke <kleinecke.oliver@googlemail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: clydebarrow <2366188+clydebarrow@users.noreply.github.com>

tests/components/usb_uart/common.yaml

@@ -42,3 +42,13 @@ usb_uart:
         baud_rate: 9600
         debug: true
         debug_prefix: "[CP210X] "
+  - id: uart_6
+    type: ft2232
+    channels:
+      - id: channel_6_1
+        baud_rate: 115200
+      - id: channel_6_2
+        baud_rate: 9600
+        stop_bits: 2
+        data_bits: 7
+        parity: odd