fix: add some logs to flaky handlers

[jtmcdole]

While testing today, I realized I can't see anything from the cloud logs.

[github-actions]

🤖 Hi @jtmcdole, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[github-actions]

## 📋 Review Summary

This PR introduces helpful logging to the flaky test handling mechanisms to improve observability. The additions are targeted and achieve the stated objective.

🔍 General Feedback

• The log additions are clear and context-rich.
• Consider avoiding logging full objects like the Issue class within collections to prevent excessive log bloat, as suggested in the inline comment.

[github-actions]

🟡 Logging the entire `nameToExistingIssue` map, which contains `Issue` objects as values, may result in verbose and hard-to-read logs since it will print the `toString()` representation of each `Issue`. Consider logging just the keys (builder names) or the total count to keep the logs clean and informative.

Suggested change

	log.info(
	'updateExistingFlakyIssue($slug): handling $nameToExistingIssue over ${builderFlakyMap.length} builders (${ignoreFlakyMap.length} ignored)',
	log.info(
	'updateExistingFlakyIssue($slug): handling ${nameToExistingIssue.keys} over ${builderFlakyMap.length} builders (${ignoreFlakyMap.length} ignored)',
	);