Add `entity_guid` to agent control health file

[amychisholm03]

Description

Agent specs PR 742 requires us to add entity_guid to the agent control health file. This is a requirement for the Feb launch.

Acceptance Criteria

• entity_guid is added to the HealthReporter class
• relevant tests are created

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-500239