Provide additional answers in NAPTR queries

[miodvallat]

Short description

This adds additional answers with replacement names found in NAPTR queries when known, and NAPTR records have the S or A flags. This is similar to what the recursor already does, and is based upon its logic.

Takes over #12966 (with @Habbie's approval)

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• ticked at least 4 boxes above

[coveralls]

Pull Request Test Coverage Report for Build 12947462684

Details

• 11 of 11 (100.0%) changed or added relevant lines in 1 file are covered.
• 45 unchanged lines in 12 files lost coverage.
• Overall coverage increased (+0.003%) to 64.702%

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Files with Coverage Reduction	New Missed Lines	%
pdns/pollmplexer.cc	1	83.66%
pdns/recursordist/aggressive_nsec.cc	2	66.32%
pdns/distributor.hh	2	51.86%
pdns/opensslsigners.cc	2	61.13%
pdns/packethandler.cc	3	73.04%
pdns/iputils.cc	3	56.07%
pdns/dnsrecords.cc	3	80.22%
pdns/recursordist/recpacketcache.hh	3	89.55%
pdns/dnsdistdist/dnsdist-lbpolicies.cc	4	70.3%
pdns/recursordist/test-syncres_cc1.cc	6	89.8%

Totals
Change from base Build 12944046345:	0.003%
Covered Lines:	127847
Relevant Lines:	166482

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💛 - Coveralls