Include additional error details when upload fails.

Description

A customer ran into an issue where the root cause was a misconfigured URL. The URL wasn't included in the error output making it more difficult to debug.

Uploading artifacts... 
target/artifact/*.file: found 3 matching files 
ERROR: Uploading artifacts to coordinator... forbidden responseStatus=403 Forbidden status=403 Forbidden
FATAL: permission denied 
ERROR: Job failed: exit code 1 

Proposal

Include URL/endpoints in error responses. (Any other details/debug that can be included?)

Links to related issues and merge requests / references

https://gitlab.com/gitlab-org/gitlab-runner/blob/master/network/gitlab.go

Internal ZD: https://gitlab.zendesk.com/agent/tickets/96576