Add system.entropy metrics

[rogercoll]

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Area(s)

area:system

Is your change request related to a problem? Please describe.

The available entropy in a system is normally monitored by cryptographic applications in order to ensure the integrity of random numbers generation.

On Linux and MacOS systems, this information can be retrieved from a file (e.g /proc/sys/kernel/random/entropy_avail), the proposed metrics would reflect all the available information about the "system entropy".

OpenTelemetry Collector Contrib issue: https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/34220

Metricbeat current metrics: https://www.elastic.co/guide/en/beats/metricbeat/current/exported-fields-system.html#_entropy_2

Describe the solution you'd like

• system.entropy.limit: the maximum amount of entropy the pool can hold (bits)
• system.entropy.(usage/available): the current amount of entropy available in the system's entropy pool (bits)
• system.entropy.utilization: fraction of usage/available out of its limit

Describe alternatives you've considered

No response

Additional context

No response