tcp_connection_duration should be measured in seconds

Nobody has claimed this yet.

We currently measure connection durations in milliseconds. It's probably more appropriate to measure connection durations in terms of seconds. In either case, we should use a histogram that makes sense for connection durations:

```
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="1"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="2"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="3"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="4"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="5"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="10"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="20"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="30"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="40"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="50"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="100"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="200"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="300"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="400"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="500"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="1000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="2000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="3000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="4000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="5000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="10000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="20000"} 0
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="30000"} 1
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="40000"} 1
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="50000"} 1
tcp_connection_duration_ms_bucket{direction="inbound",peer="src",tls="true",errno="ENOTCONN",le="+Inf"} 5
tcp_connection_duration_ms_count{direction="inbound",peer="src",tls="true",errno="ENOTCONN"} 5
tcp_connection_duration_ms_sum{direction="inbound",peer="src",tls="true",errno="ENOTCONN"} 28334607
```

Start by locating the tcp_connection_duration metric and its histogram definition in the Linkerd2 repository. Review the sample Prometheus output in this issue, then determine the seconds-based name and bucket ranges; done means connection durations are reported in seconds with a histogram appropriate to their observed scale.

Written by the indexing model from the issue text.