* mDNS: Fix build against LwIP 2.2.0
* Stop defining ip_addr_t when !CONFIG_IPV6
The only reason we had to do this is because we forgot to define LWIP_IPV4,
which is fixed in our LwIP port now, but keep it around for !CONFIG_IPV6
for now for builds against older LwIP.
* Allow returning IPv6 results from WiFiClass::hostByName()
* Add ipv6 and extra mDNS files for LwIP 2.2.0
* Add IPv6 support to BK72xx WifiSTA
Add an allLocalIPv6() method to return a *vector* of addresses, rather
than just one. It's not clear where the enableIpV6() and localIPv6()
methods came from; they don't seem to be part of the standard Arduino
class.
Eventually at least for ESPHome, I'd like to stop using these classes
and just let the ESPHome wifi component talk directly to LwIP. Or maybe
LibreTiny should offer an API compatible with the esp-idf one which is
a light wrapper around LwIP.
But short of a major refactor, this seems like a reasonable option.
* Update LwIP default to 2.2.0
* Apply suggestions from code review
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Co-authored-by: Kuba Szczodrzyński <kuba@szczodrzynski.pl>
