[rfc] remove (part of?) selftest --benchmark and bzrlib.benchmarks

[Martin Pool]

We added, a while ago, the 'bzr selftest --benchmark' facility.  These
are benchmarks that primarily exercise particular apis (therefore
microbenchmarks not macrobenchmarks), and they mostly (only?) measure
elapsed time not effort.

It was a good thing to try, but my impression is that it hasn't turned
out very well, and other benchmarking efforts have worked better, so
perhaps it's time to remove them in the interests of tidiness.

I do see people running microbenchmarks using timeit or shell scripts,
and running usertest for overall operations, or writing deterministic
effort tests of APIS, and all of them sound good.  benchmarks that
don't give a red-green result and that measure just one small part of
the picture don't seem worth keeping around in the long term.

I don't see any substantial commits in that directory for a very long
time.  Does anyone still run them?

-- 
Martin <http://launchpad.net/~mbp/>