fix: fix infra-host definition so it uses the EC2 instanceId as the identifier of the entity

[jsubirat]

Relevant information

This PR modifies the synthesis rule of HOST entities only for Log datapoints (feature currently not being used). The identifier of HOST entities needs to be aligned with the identifier used by the Metric Streams integration, which also uses the instanceId as the identifier as opposed to the ARN.

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.