Fix io_counters import issue

[rads-1996]

Description

Fixes - #45283

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

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• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

[Copilot]

Pull request overview

This PR addresses startup/import failures in azure-monitor-opentelemetry-exporter performance counters caused by psutil.Process().io_counters() raising (e.g., AccessDenied) during module import, and adds a regression test to validate the fallback behavior.

Changes:

• Guard module-level initialization of I/O counters to avoid import-time failures when psutil I/O counters are unavailable or inaccessible.
• Add a unit test that re-executes the module under a patched psutil.Process to simulate AccessDenied at import time.
• Document the fix in the package CHANGELOG.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
sdk/monitor/azure-monitor-opentelemetry-exporter/azure/monitor/opentelemetry/exporter/_performance_counters/_manager.py	Adds exception handling around initial I/O counters read to prevent import-time crashes.
sdk/monitor/azure-monitor-opentelemetry-exporter/tests/performance_counters/test_performance_counters.py	Adds regression test using runpy + patched psutil.Process to validate import-time fallback.
sdk/monitor/azure-monitor-opentelemetry-exporter/CHANGELOG.md	Adds a Bugs Fixed entry for the import issue.