Add custom verification handler to NIOSSLServerHandler #2153

Job	Run time
linux (swift:5.9)	3m 41s
linux (swift:5.10)	3m 39s
linux (swift:6.0)	4m 5s
linux (swiftlang/swift:nightly-6.1-jammy)	4m 56s
	16m 21s

Provide feedback