Description

Adds support for the process.disk.io metric to opentelemetry-instrumentation-system-metrics.

Fixes #3647

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Added unit tests for process.disk.io:

• test_process_disk_io — verifies read_bytes and write_bytes are collected correctly
• test_process_disk_io_not_implemented_error — verifies graceful handling on platforms where io_counters() is unavailable (e.g. macOS)

Run locally with:
pytest tests/test_system_metrics.py -v -k "disk_io or process_metrics_instrument"
Result: 42 passed, 1 skipped, 0 failed

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated