feat(client): implement Clone for Tunnel #667

Job	Run time
Check Style	7s
semver	28s
Test with Miri	50s
Check MSRV (1.63)	3m 53s
Test stable on windows-latest	1m 50s
features	39s
Test stable on macos-latest	32s
Test beta on ubuntu-latest	40s
Test nightly on windows-latest	1m 30s
Test stable on ubuntu-latest	41s
Test beta on macos-latest	52s
Test beta on windows-latest	1m 14s
Test nightly on macos-latest	47s
Test nightly on ubuntu-latest	35s
Build docs	13s
CI is green	3s
	14m 54s

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