Optimize issue lookup in UpgradeDependencies task

[lucasrmendonca7]

Replace linear search with HashMap lookup in UpgradeDependencies.findExistingUpgradeIssue

This PR refactors the issue lookup logic in UpgradeDependencies to use a HashMap instead of a linear search, reducing the algorithmic complexity from O(N * M) to O(N + M).

Problem

The method findExistingUpgradeIssue iterates through the entire list of existing issues for each upgrade, resulting in O(N * M) complexity where N is the number of upgrades and M is the number of existing issues. While functionally correct, this pattern doesn't scale well and doesn't clearly express the intent of finding an issue by its title.

Solution

• Pre-index existing upgrade issues into a HashMap<String, Issue> keyed by normalized title, at a cost of O(M).
• Replace the loop in findExistingUpgradeIssue with a direct Map.get() call, reducing the per-upgrade lookup from O(M) to O(1).
• Change method signature to accept Map<String, Issue> instead of List<Issue>.
• Overall complexity reduced from O(N * M) to O(N + M).

Why this is better

• Complexity: O(N * M) → O(N + M)
• Intent: A map clearly signals "I want to find an issue by its title"
• Readability: One line instead of a loop with string manipulation
• Consistency: Follows the principle of using the right data structure for the job

Testing

All existing tests in buildSrc pass successfully.

[snicoll]

Thanks but we don't need to optimize this. The issue you described is impactful with a large number of issues and irrelevant for what this part of the code handles.