[Java][HttpClient] Fix memory leak with virtual threads (#21729) (#21… #981

Job	Run time
Build Java Client JDK8 (samples/client/echo_api/java/feign-gson)	1m 3s
Build Java Client JDK8 (samples/client/echo_api/java/apache-httpclient)	1m 16s
Build Java Client JDK8 (samples/client/echo_api/java/resttemplate)	1m 15s
Build Java Client JDK8 (samples/client/echo_api/java/resteasy)	57s
Build Java Client JDK8 (samples/client/echo_api/java/okhttp-gson)	1m 3s
	5m 34s

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