NMS-19586: Improve enlinkd performance

[JSimo]

• Stop CPU spinning by switching the scheduling to be delay based
• Improve performance for lookup by including an hashmap

Previously enlinkd has been considered an performance heavy feature, it was figured out with the use of flamegraphs that the feature mostly kept 1 CPU core fully loaded with an classic spin loop. This commit targets fixed to fix that.

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External References

• Jira (Issue Tracker): https://opennms.atlassian.net/browse/NMS-19586

[rssntn67]

This PR looks good for me.