nsq_to_file: update to use a PCRE-style regex to support including lookaheads and backreferences in a topic-pattern to allow for wildcard archiving with exclusions

[danbf]

addresses issue: #1517

Right now nsq_to_file only supports RE2 style regex's in

nsq/apps/nsq_to_file/topic_discoverer.go

Line 99 in 51470ca

match, err := regexp.MatchString(t.opts.TopicPattern, topic)

through the use of the built-in golang regexp.MatchString. This prevents the use of wildcard archiving with exclusions which is a use case we have.

So a topic pattern like .* works but one like ^(?!not_so_important_events$)[a-z0-9_]+$ which would ignore the topic not_so_important_events doesn't work since it requires lookaheads which RE2 does not permit.
like: https://regex101.com/r/4S2pGx/1

Added the https://github.com/philipprochazka/regexp2 library and used it for this regex in

nsq/apps/nsq_to_file/topic_discoverer.go

Line 99 in 51470ca

match, err := regexp.MatchString(t.opts.TopicPattern, topic)