[FLINK-38961][metrics] Display process metrics (CPU, Memory, I/O) on TaskManager Web UI

[spuru9]

What is the purpose of the change

This pull request surfaces the TaskManager process's own resource usage (CPU, memory and disk I/O) as Flink metrics and displays them on the TaskManager Web UI.

When metrics.system-resource is enabled, SystemResourcesCounter now additionally collects the TaskManager process's CPU usage, resident set size and disk bytes read/written via OSHI, exposing them as the Process.CPU.Usage, Process.Memory.RSS, Process.IO.Read and Process.IO.Write gauges. A new "Process Usage" panel on the TaskManager metrics page renders these values.

Brief change log

• SystemResourcesCounter collects per-process CPU usage, RSS and disk read/written bytes via OSHI
• SystemResourcesMetricsInitializer registers the new Process.* gauges
• Added a "Process Usage" panel to the TaskManager metrics page in the Web UI, querying the new gauges over the REST API
• Documented the new metrics in docs/content/docs/ops/metrics.md and the zh translation

Verifying this change

This change added unit-test coverage in SystemResourcesCounterTest and can additionally be verified as follows:

• Start a cluster with metrics.system-resource: true, open the TaskManager metrics page and confirm the new "Process Usage" panel shows CPU, memory (RSS) and combined I/O.

Note: per-process I/O is only populated on platforms where OSHI supports it (e.g. Linux via /proc); on macOS these counters report 0.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no (OSHI is already a Flink dependency)
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? docs (metrics.md, en + zh)

---

Was generative AI tooling used to co-author this PR?

• Yes (Claude Code)

Generated-by: Claude Code

[flinkbot]

CI report:

• da80be4 Azure: SUCCESS

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