Improve custom hook error logging

Previously if a custom hook failed, it would be difficult to determine which hook in question were actually failing without using strace. The failing hook could be global or a project hook. We now log the filename along with the error message.

Relates to #2923 (closed)

Previous error

{
  "correlation_id": "01FMXEDMS5RNX4K2MGYYFC2RQY",
  "error": "executing custom hooks: exit status 1",
  "grpc.meta.deadline_type": "none",
  "grpc.meta.method_type": "bidi_stream",
  "grpc.method": "PreReceiveHook",
  "grpc.request.fullMethod": "/gitaly.HookService/PreReceiveHook",
  "grpc.request.glProjectPath": "root/another-import",
  "grpc.request.glRepository": "project-64",
  "grpc.request.repoPath": "@hashed/a6/8b/a68b412c4282555f15546cf6e1fc42893b7e07f271557ceb021821098dd66c1b.git",
  "grpc.request.repoStorage": "default",
  "grpc.service": "gitaly.HookService",
  "grpc.start_time": "2021-11-20T01:12:25.790",
  "level": "warning",
  "msg": "stopping transaction because pre-receive hook failed",
  "peer.address": "@",
  "pid": 224209,
  "span.kind": "server",
  "system": "grpc",
  "time": "2021-11-20T01:12:25.867Z"
}

New error

{
  "correlation_id": "01FMXEQPQKSS8B108XKQDYFD0B",
  "error": "executing custom hooks: error executing \"/var/opt/gitlab/gitaly/custom_hooks/pre-receive.d/pre-receive\": exit status 1",
  "grpc.meta.deadline_type": "none",
  "grpc.meta.method_type": "bidi_stream",
  "grpc.method": "PreReceiveHook",
  "grpc.request.fullMethod": "/gitaly.HookService/PreReceiveHook",
  "grpc.request.glProjectPath": "root/another-import",
  "grpc.request.glRepository": "project-64",
  "grpc.request.repoPath": "@hashed/a6/8b/a68b412c4282555f15546cf6e1fc42893b7e07f271557ceb021821098dd66c1b.git",
  "grpc.request.repoStorage": "default",
  "grpc.service": "gitaly.HookService",
  "grpc.start_time": "2021-11-20T01:17:55.748",
  "level": "warning",
  "msg": "stopping transaction because pre-receive hook failed",
  "peer.address": "@",
  "pid": 1421048,
  "span.kind": "server",
  "system": "grpc",
  "time": "2021-11-20T01:17:55.831Z"
}