influxdb3: Include node ID and modes as metrics labels

Include node ID and modes as metrics labels so that the user doesn't need to do additional processing (e.g. capture hostname and relabel) to identify the source.

This is more valuable for Enterprise nodes and probably not relevant for Core.

Suggested output:

```
http_requests_total{node_id="abc123",node_mode="ingester,querier",method="GET",method_path="GET /metrics",path="/metrics",status="ok"} 42
```

Current (v3.5.0) output:

```
http_requests_total{method="GET",method_path="GET /metrics",path="/metrics",status="ok"} 10
```

_Issue raised in https://github.com/influxdata/docs-v2/pull/6422#discussion_r2389221910_:

> So these metrics are specific to each node. Does the prometheus schema include the node ID or is there additional processing a user would have to do to know the source node?

Start by locating the Prometheus metrics generation for http_requests_total and inspect how its existing method, method_path, path, and status labels are defined. Add node_id and node_mode labels for the node-specific metrics, then verify the output matches the suggested schema, especially for Enterprise nodes.

Written by the indexing model from the issue text.