dnsdist: Implement OTLP RemoteLogger

[pieterlexis]

Short description

This PR adds another kind of RemoteLogger, namely one for OTLP.

At the moment, it is only hooked up for dnsdist's traces. When using OpenTelemetry tracing, this logger and the SetTrace action, the DNS processing thread will send the Trace object to this Logger. This means that the protobuf serialization is handled in the RemoteLogger thread, freeing the DNS processing thread for real work.

I've opened this PR as a draft for early review and for the CI to do its thing.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• 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)

[coveralls]

Coverage Report for CI Build 28383531898

Coverage decreased (-0.05%) to 71.089%

Details

• Coverage decreased (-0.05%) from the base build.
• Patch coverage: 79 uncovered changes across 6 files (131 of 210 lines covered, 62.38%).
• 149 coverage regressions across 16 files.

Uncovered Changes

File	Changed	Covered	%
pdns/dnsdistdist/otlp_logger.cc	106	70	66.04%
pdns/dnsdistdist/otlp_logger.hh	19	0	0.0%
pdns/dnsdistdist/dnsdist-lua-bindings-protobuf.cc	14	1	7.14%
pdns/dnsdistdist/protozero-otlp.hh	29	22	75.86%
pdns/dnsdistdist/dnsdist-configuration-yaml.cc	20	17	85.0%
pdns/dnsdistdist/dnsdist-lua-configuration-items.cc	2	1	50.0%
Total (7 files)	210	131	62.38%

Coverage Regressions

149 previously-covered lines in 16 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
modules/geoipbackend/geoipinterface-mmdb.cc	73	7.89%
pdns/recursordist/rec-system-resolve.cc	19	49.32%
pdns/recursordist/rec-tcp.cc	10	70.33%
pdns/opensslsigners.cc	9	61.47%
pdns/recursordist/syncres.cc	8	81.18%
pdns/recursordist/pdns_recursor.cc	5	75.65%
pdns/auth-secondarycommunicator.cc	4	57.94%
pdns/packethandler.cc	4	69.13%
pdns/communicator.cc	3	64.1%
pdns/iputils.cc	3	60.18%

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Coverage Stats

Relevant Lines:	171671
Covered Lines:	133766
Line Coverage:	77.92%
Relevant Branches:	82076
Covered Branches:	46619
Branch Coverage:	56.8%
Branches in Coverage %:	Yes
Coverage Strength:	5388015.99 hits per line

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💛 - Coveralls