Add support for custom tls server names. (#22372) #1031

Job	Run time
Build Java Client JDK8 (samples/client/echo_api/java/okhttp-gson)	1m 19s
Build Java Client JDK8 (samples/client/echo_api/java/apache-httpclient)	1m 22s
Build Java Client JDK8 (samples/client/echo_api/java/resttemplate)	1m 28s
Build Java Client JDK8 (samples/client/echo_api/java/feign-gson)	1m 24s
Build Java Client JDK8 (samples/client/echo_api/java/resteasy)	1m 19s
	6m 52s

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