ZOOKEEPER-4983: Add client-triggered operation count metrics #2905

Job	Run time
Typo Check	8s
mvn (full-build-cppunit-tests, 11, -Pfull-build verify -Dtest=_ -DfailIfNoTests=false)	10m 32s
mvn (full-build-jdk11, 11, -Pfull-build apache-rat:check verify -DskipTests spotbugs:check checks...	1m 50s
mvn (full-build-java-tests, 11, -Pfull-build verify -Dsurefire-forkcount=1 -DskipCppUnit -Dsurefi...	1h 8m 6s
mvn (full-build-jdk8, 8, -Pfull-build apache-rat:check verify -DskipTests spotbugs:check checksty...	1m 45s
	1h 22m 21s

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