pdns: emit rrsig on alias responses #20837

Job	Run time
Analyze (cpp, rec)	29m 59s
Analyze (cpp, dnsdist)	33m 10s
Force failure in case there are binaries present in a pull request	6s
Check formatting of Python scripts	15s
Analyze (cpp, auth)	32m 9s
Check whether clang-tidy succeeded	3s
	1h 35m 42s

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