JOBS-2089: Add RTFS metrics source in log-analytics-splunk

[hramisetty]

Add RTFS (Real-Time File Store) metrics collection support to the Artifactory fluentd config for Splunk. This enables scraping metrics from the RTFS endpoint at artifactory/service/rtfs/api/v1/metrics and forwarding them to Splunk with the jfrog.rtfs metric prefix.

Changes:

• Add RTFS source block in fluent.conf.rt with target_platform SPLUNK
• Add explicit target_platform to existing Artifactory source block
• Update README with RTFS metrics documentation
• Update CHANGELOG with new version entry

Requires fluent-plugin-jfrog-metrics >= 0.2.16
Parent ticket: JOBS-1897

Testing Done:
Container: jfrog-fluentd-splunk-rt + splunk-test (local Splunk Enterprise)
Fluentd logs:

[info]: [metrics_http_jfrt] Executing jfrog.rtfs metrics collection from: http://host.docker.internal:8082/rtfs/api/v1/metrics
[info]: [metrics_http_jfrt] jfrog.rtfs metrics were successfully collected from url: http://host.docker.internal:8082/rtfs/api/v1/metrics
[info]: [metrics_http_jfrt] Timer task Execution successfully returned

Splunk mstats query:

| mstats latest(_value) as value WHERE index="jfrog_splunk_metrics" AND metric_name="jfrog.rtfs.*" BY metric_name

Result: 148 unique RTFS metrics. Sample:

metric_name	value
jfrog.rtfs.application_ready_time_seconds	18.218
jfrog.rtfs.application_started_time_seconds	5.931
jfrog.rtfs.disk_free_bytes	864835551232
jfrog.rtfs.disk_total_bytes	977896124416
jfrog.rtfs.executor_active_threads	0
jfrog.rtfs.grpc_server_received_total	2
jfrog.rtfs.hikaricp_connections	3

UI: