feat: Add haproxy apm relationship definitions

[muruganishekar]

Relevant information

Api Review Board (ARB)

Any pull request with changes to this repository has to be linked with an ARB ticket, which has to be approved before merging.

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ARB Jira ticket:
https://new-relic.atlassian.net/browse/NR-XXXX

Checklist

• I've read the guidelines and understand the acceptance criteria.
• The value of the attribute marked as identifier will be unique and valid.
• I've confirmed that my entity type wasn't already defined. If it is I'm providing an explanation above.
• I've linked an ARB ticket & received approval from API Review Board in order to make these changes

[entityBot]

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I have found some errors processing these changes:

• No valid, approved ARB ticket found in the PR description. This PR has to be reviewed by the API Review Board, please include a link to the ticket of that review in the PR description. Check how to start the process here or reach #api-review-board channel in case of doubts