sdkconfig: Add CONFIG_LWIP_IPV6_AUTOCONFIG for IPv6 SLAAC

To use IPv6 we need proper SLAAC support which is not possible without this option.
Compile tested on esp32, esp32s2, esp32s3, esp32c3
Functionality tested in esp32 BasicHttpClient with some minor patches, IPv6 start to work.

No significant sketch size increase (probably within rounding bounds):
Before:
Wrote 875328 bytes (558896 compressed) at 0x00010000 in 9.0 seconds (effective 779.4 kbit/s)...
After:
Wrote 875328 bytes (558942 compressed) at 0x00010000 in 9.0 seconds (effective 779.8 kbit/s)...

This patch part of the efforts mentioned in espressif/arduino-esp32#6242

Proper IPv6 support also was requested in:
espressif/arduino-esp32#6626
espressif/arduino-esp32#6590
espressif/arduino-esp32#6283
espressif/arduino-esp32#6703
espressif/arduino-esp32#5624
espressif/arduino-esp32#1261
And many others.

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

configs/defconfig.common

@@ -1,3 +1,4 @@
 CONFIG_AUTOSTART_ARDUINO=y
 CONFIG_ARDUINO_UDP_RUN_CORE0=y
-# CONFIG_WS2812_LED_ENABLE is not set
+# CONFIG_WS2812_LED_ENABLE is not set
+CONFIG_LWIP_IPV6_AUTOCONFIG=y