improve: Enrich GC metrics to better analyze GC behavior and the time consumption of each phase.

[ethqunzhong]

Motivation

Enrich GC metrics to better analyze GC behavior and the time consumption of each phase.

In our online environment, we found that some clusters spend a lot of time scanning metadata during gc, so the newly added metrics can more conveniently help us analyze the cluster gc behavior

this PR add 4 new metrics: bookie_GC_LEDGER_RUNTIME bookie_EXTRACT_META_RUNTIME bookie_COMPACT_RUNTIME bookie_ENTRY_LOG_COMPACT_RATIO

Changes

• bookie_GC_LEDGER_RUNTIME operation stats of doing gc ledgers based on metaStore, Time consumption for comparing ledger meta between local and metadata store (zk).

• bookie_EXTRACT_META_RUNTIME Time consumption for extracting Meta from entryLogs.

• bookie_COMPACT_RUNTIME Time consumption of entry log compaction.

• bookie_ENTRY_LOG_COMPACT_RATIO Current proportion of compacted entry log files that have been executed (Provide reference for users when setting CompactionThreshold values, and configure more reasonable values)