samd/boards/ADAFRUIT_METRO_M4_EXPRESS: Add Metro M4 Express Airlift.

The board files can be used for both Adafruit Metro M4 variants.  The Wifi
support is in progress.

ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/board.json

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+{
+    "deploy": [
+        "../deploy.md"
+    ],
+    "docs": "",
+    "features": [
+        "Micro USB",
+        "ADC",
+        "DAC",
+        "RGB LED",
+        "QSPI Flash",
+        "WiFi",
+        "BLE",
+        "JLink"
+    ],
+    "images": [
+        "metro_m4_express_airlift.jpg"
+    ],
+    "mcu": "samd51",
+    "variants": {
+        "wlan": "WLAN without SSL support"
+    },
+    "product": "Metro M4 Express Airlift",
+    "thumbnail": "",
+    "url": "https://www.adafruit.com/product/4000",
+    "vendor": "Adafruit"
+}

ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/mpconfigboard.h

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+#define MICROPY_HW_BOARD_NAME               "Metro M4 Express Airlift"
+#define MICROPY_HW_MCU_NAME                 "SAMD51J19A"
+
+#define MICROPY_HW_XOSC32K                  (1)
+#define MICROPY_HW_QSPIFLASH                GD25Q16C
+
+// defines for WLAN
+#define MICROPY_HW_WIFI_SPI_ID              (2)
+#define MICROPY_HW_WIFI_SPI_BAUDRATE        (8000000)
+
+#define MICROPY_HW_WIFI_SPI_SCK             (13)
+#define MICROPY_HW_WIFI_SPI_MOSI            (12)
+#define MICROPY_HW_WIFI_SPI_MISO            (14)
+
+#define MICROPY_HW_NINA_ACK                 (36)
+#define MICROPY_HW_NINA_GPIO1               (15)
+#define MICROPY_HW_NINA_RESET               (37)
+// #define MICROPY_HW_NINA_GPIO0               (33)
+
+// defines for BLE
+#define MICROPY_PY_BLUETOOTH_NINAW10        (1)
+
+#define MICROPY_HW_BLE_UART_ID              (0)
+#define MICROPY_HW_BLE_UART_BAUDRATE        (115200)
+
+#define MICROPY_HW_BLE_UART_TX              (4)
+#define MICROPY_HW_BLE_UART_RX              (7)
+
+#define MICROPY_HW_NINA_RTS                 (12)
+#define MICROPY_HW_NINA_CTS                 (36)

ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/mpconfigboard.mk

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+MCU_SERIES = SAMD51
+CMSIS_MCU = SAMD51J19A
+LD_FILES = boards/samd51x19a.ld sections.ld
+TEXT0 = 0x4000
+
+# MicroPython settings
+MICROPY_VFS_LFS1 ?= 1
+
+MICROPY_PY_NETWORK ?= 1
+MICROPY_PY_NETWORK_NINAW10 ?= 1
+
+BOARD_VARIANTS += "wlan"

ports/samd/boards/ADAFRUIT_METRO_M4_EXPRESS/pins.csv

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+# Pin rows contain Pin number and pin name.
+# Pin rows start with PIN_
+# If the pin name is omitted, the pin number is added as name.
+# Empty lines and lines not starting with PIN_ are ignored
+
+PIN_PA02,A0
+PIN_PA05,A1
+PIN_PA06,A2
+PIN_PB00,A3
+PIN_PB08,A4
+PIN_PB09,A5
+PIN_PA03,AREF
+
+PIN_PA23,D0
+PIN_PA22,D1
+PIN_PB17,D2
+PIN_PB16,D3
+PIN_PB13,D4
+PIN_PB14,D5
+PIN_PB15,D6
+PIN_PB12,D7
+PIN_PA21,D8
+PIN_PA20,D9
+PIN_PA18,D10
+PIN_PA19,D11
+PIN_PA17,D12
+PIN_PA16,D13
+
+PIN_PB02,SDA
+PIN_PB03,SCL
+
+PIN_PA13,SCK
+PIN_PA12,MOSI
+PIN_PA14,MISO
+
+PIN_PB22,NEOPIXEL
+PIN_PB06,RXLED
+PIN_PB07,TXLED
+
+# Airlift
+PIN_PB05,ESP_RESET
+PIN_PB04,ESP_BUSY
+PIN_PA15,ESP_CS
+PIN_PB01,ESP_GPIO0
+PIN_PA07,ESP_RX
+PIN_PA04,ESP_TX
+PIN_PB23,ESP_RTS
+
+# QSPI flash
+PIN_PA08,FLASH_MOSI
+PIN_PA09,FLASH_MISO
+PIN_PA10,FLASH_WP
+PIN_PA11,FLASH_HOLD
+PIN_PB10,FLASH_SCK
+PIN_PB11,FLASH_CS
+
+# USB
+PIN_PA24,USB_DM
+PIN_PA25,USB_DP
+PIN_PA26,USB_SOF
+PIN_PA17,USB_HOSTEN
+
+# JLink
+PIN_PA30,SWCLK
+PIN_PA31,SWDIO
+PIN_PB30,SWO