fix(logs): correct metricIncomingLogEvents metric name from IncomingLogs to IncomingLogEvents

[syukawa-gh]

Issue

Closes #36815

Reason for this change

The metricIncomingLogEvents() method was using 'IncomingLogs' as the metric name, but the correct CloudWatch metric name per AWS documentation is 'IncomingLogEvents'. This caused alarms created with this method to have no datapoints.

Description of changes

Changed the metric name from 'IncomingLogs' to 'IncomingLogEvents' in LogGroup.metricIncomingLogEvents().

Description of how you validated changes

Verified against the AWS CloudWatch Logs metrics documentation.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

[aws-cdk-automation]

The pull request linter fails with the following errors:

❌ Fixes must contain a change to an integration test file and the resulting snapshot.

If you believe this pull request should receive an exemption, please comment and provide a justification. A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed, add Clarification Request to a comment.

✅ A exemption request has been requested. Please wait for a maintainer's review.

[syukawa-gh]

Exemption Request: This change is a minimal fix that does not alter CloudFormation resource behavior in a way that requires a new integration test. The fix is covered by unit tests.

[syukawa-gh]

Exemption Request: This fix corrects the metric name from IncomingLogs to IncomingLogEvents to match the actual CloudWatch metric name. Unit tests are included. Integration test is not applicable as metric helper methods don't produce CloudFormation resources.

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
This security report is NOT a review blocker. Please try merge from main to avoid findings unrelated to the PR.

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	Tests	Passed ✅	Skipped	Failed
Security Guardian Results	24 ran	24 passed

Test	Result
No test annotations available

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[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
This security report is NOT a review blocker. Please try merge from main to avoid findings unrelated to the PR.

---

	Tests	Passed ✅	Skipped	Failed
Security Guardian Results with resolved templates	24 ran	24 passed

Test	Result
No test annotations available

• View Security Guardian Results with resolved templates