[cli] add Doxygen for SRP server (#9653) #1477

Job	Run time
backbone-router	13m 41s
BR (mDNSResponder, TREL=0)	28m 0s
BR (mDNSResponder, TREL=1)	26m 22s
BR MATN (mDNSResponder, TREL=0)	18m 33s
BR LowPower (mDNSResponder, TREL=0)	7m 50s
BR nat64 openthread (mDNSResponder, TREL=0)	23m 37s
BR (avahi, TREL=0)	26m 18s
BR (avahi, TREL=1)	25m 59s
BR core firewall (avahi, TREL=0)	26m 22s
upload-coverage	2m 6s
delete-coverage-artifacts	5s
	3h 18m 53s

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