[reciever/haproxy] Many ResourceMetrics emitted with the same resource

[dmitryax]

The receiver emits multiple resource metrics for each line in HAProxy stats. But they are all emitted with the same resource with only one attribute haproxy.addr set to the configured endpoint. proxy_name and service_name resource attributes (btw the names are also incorrect from OTel semantics perspective) are also supposed to be set, but they are marked as optional in metadata.yaml, so they are ignored by default.

[github-actions]

Pinging code owners for receiver/haproxy: @atoulme @MovieStoreGuy. See Adding Labels via Comments if you do not have permissions to add labels yourself.