JOBS-2092: Add RTFS metrics support in log-analytics-prometheus

[hramisetty]

Add RTFS (Real-Time File Store) metrics collection support via a tail source and Prometheus filter in the Artifactory fluentd metrics config. RTFS metrics are read from rtfs-metrics.log and exposed as Prometheus gauge metrics with the service:rtfs label.

Changes:

• Add RTFS metrics tail source in fluent_metrics.conf.rt
• Add Prometheus filter with RTFS-specific gauge metrics
• Update README with RTFS metrics documentation
• Update CHANGELOG with new version entry

Parent ticket: JOBS-1897

Testing Done:
Container: jfrog-fluentd-prometheus-rt
Test method: Injected RTFS metrics into rtfs-metrics.log (simulating Artifactory), then scraped Fluentd's Prometheus endpoint.
Command:

curl http://localhost:24231/metrics | grep rtfs

Result -- all 11 RTFS gauges exposed with service="rtfs" label:

jfrt_rtfs_runtime_heap_freememory_bytes{agent="fluentd",host="...",service="rtfs"} 536870900.0
jfrt_rtfs_runtime_heap_maxmemory_bytes{agent="fluentd",host="...",service="rtfs"} 1073741824.0
jfrt_rtfs_runtime_heap_totalmemory_bytes{agent="fluentd",host="...",service="rtfs"} 838860800.0
jfrt_rtfs_db_connections_active_total{agent="fluentd",host="...",service="rtfs"} 3.0
jfrt_rtfs_db_connections_idle_total{agent="fluentd",host="...",service="rtfs"} 7.0
jfrt_rtfs_storage_current_total_size_bytes{agent="fluentd",host="...",service="rtfs"} 536870912.0
app_rtfs_disk_used_bytes{agent="fluentd",host="...",service="rtfs"} 10737418240.0
app_rtfs_disk_free_bytes{agent="fluentd",host="...",service="rtfs"} 96636764160.0
sys_rtfs_memory_used_bytes{agent="fluentd",host="...",service="rtfs"} 4294967296.0
sys_rtfs_memory_free_bytes{agent="fluentd",host="...",service="rtfs"} 12884901888.0
sys_rtfs_cpu_ratio{agent="fluentd",host="...",service="rtfs"} 0.25

UI: The Prometheus /metrics endpoint is the raw scrape target - in a real deployment, Prometheus scrapes this and Grafana visualizes it.