Convert the errorText accumulator inside validateServerConfig to the
typed configValidator pattern. Each rule violation now renders as a
multi-line block naming the YAML key, the value the operator wrote,
and a hint pointing at the resolution. The dns.extra_records mutex
that previously crashed via log.Fatal is folded into the same
collector so an operator sees every problem in one go instead of
fixing them one startup attempt at a time.
Test wantErr assertions on validation output switch to substring
match because the rendered errors are now multi-line.
Updates #3227
Kristoffer Dalby
1b4b79901a