dnsdist-1.9.x: Backport of #13851 - tcpiohandler: Use server preference algoritm for ALPN selection

[rgacogne]

Short description

Backport of #13851.

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)
• checked that this code was merged to master

[coveralls]

Pull Request Test Coverage Report for Build 8340370679

Details

• 21 of 23 (91.3%) changed or added relevant lines in 3 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.004%) to 55.497%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pdns/tcpiohandler.cc	10	12	83.33%

Files with Coverage Reduction	New Missed Lines	%
pdns/misc.cc	2	40.56%

Totals
Change from base Build 8262456785:	0.004%
Covered Lines:	47440
Relevant Lines:	64961

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💛 - Coveralls