Missing error.message tag on router span for all traces where there is a broken pipe error

[danpayne17]

Describe the bug
When the caller closes the connection to the router before it is done sending the response, the trace that is sent to DataDog is missing the error.message tag on the router span. This is causing DataDog to be unable to display the cause of the error

To Reproduce
Steps to reproduce the behavior:

1. Connect the router to DataDog
2. Launch router with a single subgraph and in the subgraph, have it wait 10 seconds when it receives the request from the router
3. Use curl to send a request to the router
4. While the request is waiting at the subgraph, cancel the curl request (ctrl-c)
5. Observe the error in DataDog and how there is no error message. Instead it displays "Missing error message and stack trace"

Expected behavior
An error message indicating the error encountered (e.g. 'Broken pipe') should be displayed in DataDog and seen in the router trace span at error.message

Router:

• OS: Amazon Linux 2023
• Router Version: 1.37.0

Additional context
Other errors (e.g. 400) seem to populate error.message just fine. It's only when there's a broken pipe that it doesn't tag set.

Errors view in DataDog:

Span tags (error key excerpted):