local: add failing test for sideband information

We do not currently generate any messages when we're counting the
objects, as might be expected from a local upload-pack. Assert that we
do call the function when working.
local: send 'counting objects' output

Pretend we have a git process at the other end by creating a similar
progress output when inserting objects into the packbuilder.
Merge pull request #2763 from libgit2/cmn/local-proto-progress

Show progress output on fetch for the local transport