Gateway HTTP Metrics inconsistently measure failed response times

[iand]

Checklist

• This is a bug report, not a question. Ask questions on discuss.ipfs.io.
• I have searched on the issue tracker for my bug.
• I am running the latest go-ipfs version or have an issue updating.

Installation method

built from source

Version

from inspection of master branch

Config

No response

Description

The per-format latency metrics added as part of #8441 are inconsistent as to whether they include failed responses or not.

gw_unixfs_file_get_duration_seconds, gw_raw_block_get_duration_seconds include timings for failed responses

gw_car_stream_get_duration_seconds, gw_unixfs_gen_dir_listing_get_duration_seconds do not include timings for failed responses

These should be consistent and my preference is that they should not include timings for failed responses (since errors will skew latency timings lower in general)

Tech note: the difference is caused by the use of http.ServeContent for serving files and blocks which does not return an error. We should pass a custom ResponseWriter that detects whether an error occurred during the write and then only record the metric if there is no error.