newrelic: refactor error logging.

* Factor out New Relic logging to DanbooruLogger class.
* Log all exceptions to New Relic, not just statement timeouts.

app/models/application_record.rb

@@ -230,9 +230,7 @@ class ApplicationRecord < ActiveRecord::Base
         connection.execute("SET STATEMENT_TIMEOUT = #{n}") unless Rails.env == "test"
         yield
       rescue ::ActiveRecord::StatementInvalid => x
-        if Rails.env.production?
-          NewRelic::Agent.notice_error(x, :custom_params => new_relic_params.merge(:user_id => CurrentUser.id, :user_ip_addr => CurrentUser.ip_addr))
-        end
+        DanbooruLogger.log(x, expected: true)
         return default_value
       ensure
         connection.execute("SET STATEMENT_TIMEOUT = #{CurrentUser.user.try(:statement_timeout) || 3_000}") unless Rails.env == "test"