objectpool: Capture fsck stderr when fetching
We have observed the git fsck
process run in rescueDanglingObjects
failing regularly. Sometimes this is because the process is taking
longer than 75 seconds and hitting its deadline, but many times we're
getting a return code. This tells us what went wrong generally, e.g. a
problem with the commit graph, refs, etc., but not the precise issue
with the repo.
To help understand what is causing these processes to fail, capture
git fsck
's stderr and include it with the error message.
Related to #4758 (closed)