resolve: remove server 'large' level

resolve: remove server 'large' level

This removes the DNS_SERVER_FEATURE_LEVEL_LARGE, and sets the EDNS0
advertised max packet size as if always in 'large' mode.

Without this, we always send out EDNS0 opts that limit response sizes
to 512 bytes, thus the remote server will never send anything larger
and will always truncate responses larger than 512 bytes, forcing us
to drop from EDNS0 down to TCP, even though one of the primary benefits
of EDNS0 is larger packet sizes.

Fixes: #20993
(cherry picked from commit 526fce97afe130f71dba3bd4646196bbb1188b82)
(cherry picked from commit 0bc9811acfd2535bf8a7a16a3903a2c22df206c9)