rust: Add a log file rotation utility
This is ported to Rust from `mercurial/loggingutil.py`.
The "builder" pattern is used to make it visible at call sites what the two
numeric parameters mean. In Python they might simply by keyword arguments.
Differential Revision: https://phab.mercurial-scm.org/D10010
#require serve
$ hg clone http://localhost:$HGPORT/ copy
abort: * (glob)
[100]
$ test -d copy
[1]
$ "$PYTHON" "$TESTDIR/dumbhttp.py" -p $HGPORT --pid dumb.pid
$ cat dumb.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/foo copy2
abort: HTTP Error 404: * (glob)
[100]
$ killdaemons.py