dns: provide events for recoverable parse errors

dns: provide events for recoverable parse errors

Add events for the following resource name parsing issues:

- name truncated as its too long
- maximum number of labels reached
- infinite loop

Currently these events are only registered when encountered, but
recoverable. That is where we are able to return some of the name,
usually in a truncated state.

As name parsing has many code paths, we pass in a pointer to a flag
field that can be updated by the name parser, this is done in
addition to the flags being set on a specific name as when logging we
want to designate which fields are truncated, etc. But for alerts, we
just care that something happened during the parse. It also reduces
errors as it won't be forgotten to check for the flags and set the
event if some new parser is written that also parses names.

Ticket: #7280