Outlier detection healthcheck UNEJECT is confusing

*Title*: *Outlier detection healthcheck UNEJECT is confusing*

*Description*:
I had the following cluster configuration, where I wanted to disable consecutive_5xx completely and only enable it for consecutive_gateway_failure :
```
"outlier_detection": {
"consecutive_5xx": 100000, // this is deliberate. I wanted to turn it off completely as I don't want it to trigger on 500s
"interval": "2s",
"base_ejection_time": "10s",
"max_ejection_percent": 33,
"enforcing_consecutive_5xx": 0, // This is also supposed to turn off consecutive_5xx
"success_rate_minimum_hosts": 2,
"success_rate_request_volume": 20,
"consecutive_gateway_failure": 3,
"enforcing_consecutive_gateway_failure": 100,
"max_ejection_time": "30s",
"max_ejection_time_jitter": "1s"
},
```

After trying to kill a instance in the cluster I would see these kind of logs in the outlier detection logs
```
{
action: EJECT
cluster_name: bounty
eject_consecutive_event: {
}
enforced: true
num_ejections: 1
timestamp: 2024-07-08T18:00:50.740Z
type: CONSECUTIVE_GATEWAY_FAILURE
upstream_url: 10.0.209.198:24467
}

{
action: UNEJECT
cluster_name: bounty
enforced: false
num_ejections: 1
secs_since_last_action: 7
timestamp: 2024-07-08T18:00:58.521Z
type: CONSECUTIVE_5XX
upstream_url: 10.0.209.198:24467
}

{
action: EJECT
cluster_name: bounty
eject_consecutive_event: {
}
enforced: true
num_ejections: 2
secs_since_last_action: 0
timestamp: 2024-07-08T18:00:58.536Z
type: CONSECUTIVE_GATEWAY_FAILURE
upstream_url: 10.0.209.198:24467
}
```

The UNEJECT coming from type CONSECUTIVE_5XX was very confusing as:

1. EJECT was triggered by Gateway failure and not 500
2. It unejected from CONSECUTIVE_5XX even though the config is set to a very high threshold and enforcing_consecutive_5xx is set to 0.
3. The log line also had `enforced: false` which should have meant it didn't action but in fact it actually did UNEJECT. The [documentation](https://www.envoyproxy.io/docs/envoy/latest/api-v3/data/cluster/v3/outlier_detection_event.proto#data-cluster-v3-outlierdetectionevent) is also confusing as it states to only be relevant for action eject, but is logged for uneject also ` If action is eject, specifies if the ejection was enforced. true means the host was ejected. false means the event was logged but the host was not actually ejected.`

It took me a while to figure out why was this happening and that in fact this was because I had my healthcheck configuration set with `unhealthy_threshold: 2` and it was the healthcheck(even if first failed, cluster was still considered healthy) that was triggering the UNEJECT and not the CONSECUTIVE_5XX. I managed to get my desired configuration by setting successful_active_health_check_uneject_host to false. It would probably have helped if the section about health checking in the docs were under ejection algorithm and not under gRPC (proposing that change under #35185)

*Expected Behaviour*
Can the logging be changed so that UNEJECT events triggered by an active health check are of type HEALTH_CHECK instead of defaulting to CONSECUTIVE_5XX?

*Relevant Links*:
https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/outlier#ejection-algorithm
https://www.envoyproxy.io/docs/envoy/latest/api-v3/data/cluster/v3/outlier_detection_event.proto#data-cluster-v3-outlierdetectionevent