Rename "GC Pauses" to "GC Time" in Pulsar JVM dashboards¬

[lhotari]

• source metric is not about GC pauses.¬
• the source metric is "jvm_gc_collection_seconds_sum" which is not the same as "GC pause"¬
• The metric is defined in Prometheus Java client¬
  • "Time spent in a given JVM garbage collector in seconds."¬
  • source code is https://github.com/prometheus/client_java/blob/e68daf23336eb5de7856df406eb1d497f51ad3be/simpleclient_hotspot/src/main/java/io/prometheus/client/hotspot/GarbageCollectorExports.java#L53¬
  • calls GarbageCollectorMXBean.getCollectionTime()¬
    • Javadoc https://docs.oracle.com/en/java/javase/11/docs/api/java.management/java/lang/management/GarbageCollectorMXBean.html#getCollectionTime()¬ "Returns the approximate accumulated collection elapsed time in milliseconds."¬
    • Stackoverflow Q&A: https://stackoverflow.com/a/44686539¬