connection_pool: fix excessive idle CPU usage while waiting for requests #1090

Job	Run time
pack_pip	13s
pack_rpm (fedora, 35)	1m 9s
pack_rpm (fedora, 34)	1m 10s
pack_deb	1m 49s
pack_rpm (fedora, 36)	1m 7s
run_tests_pip_package_linux	2m 38s
run_tests_pip_package_windows	3m 48s
run_tests_rpm (fedora, 34)	5m 27s
run_tests_rpm (fedora, 35)	4m 45s
run_tests_rpm (fedora, 36)	5m 31s
run_tests_deb (debian, bookworm)	2m 59s
run_tests_deb (debian, bullseye)	2m 44s
run_tests_deb (ubuntu, jammy)	3m 7s
run_tests_deb (ubuntu, noble)	2m 48s
run_tests_deb (ubuntu, focal)	2m 52s
publish_pip	-1s
publish_deb	-1s
publish_rpm	-1s
	42m 4s

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