dnsdist: Gather Server Name Indication on QUIC (DoQ, DoH3) connections

[rgacogne]

Short description

This PR adds Server Name Indication support for incoming QUIC (DoQ, DoH3) connections. It requires an accessor in the Quiche library that has not been merged yet, see cloudflare/quiche#1895

Closes #14048.

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)

[rgacogne]

CI failure as expected since our version of Quiche lacks the required accessor:

FAILED test_SNI.py::TestSNI::testServerNameIndication - AssertionError: None is not true

[rgacogne]

The accessor has been added to Quiche 🥳

[rgacogne]

CI failure as expected since our version of Quiche lacks the required accessor

I have now gated the parts of this test that require the accessor behind the ENABLE_SNI_TESTS_WITH_QUICHE environment variable, and I'll create an issue to remember to enable it (or remote the gate?) once a new version of Quiche is available.

[coveralls]

Pull Request Test Coverage Report for Build 12926347037

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 26 of 26 (100.0%) changed or added relevant lines in 3 files are covered.
• 46 unchanged lines in 12 files lost coverage.
• Overall coverage increased (+0.03%) to 64.733%

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Files with Coverage Reduction	New Missed Lines	%
pdns/recursordist/aggressive_nsec.cc	2	66.39%
pdns/dnsdistdist/dnsdist.cc	2	68.87%
pdns/recursordist/test-syncres_cc2.cc	3	88.85%
pdns/recursordist/syncres.cc	3	80.23%
pdns/misc.cc	3	62.77%
pdns/fstrm_logger.cc	3	44.08%
pdns/recursordist/recpacketcache.hh	3	89.55%
pdns/shuffle.cc	4	53.93%
pdns/recursordist/test-syncres_cc1.cc	5	89.84%
pdns/signingpipe.cc	5	83.91%

Totals
Change from base Build 12925097496:	0.03%
Covered Lines:	127873
Relevant Lines:	166459

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💛 - Coveralls