bisect: fix output regressions in v2.30.0

bisect: fix output regressions in v2.30.0

When d1bbbe45df8 (bisect--helper: reimplement `bisect_run` shell
function in C, 2021-09-13) reimplemented parts of "git bisect run" in
C it changed the output we emitted so that:

 - The "running ..." line was now quoted
 - We lost the \n after our output
 - We started saying "bisect found ..." instead of "bisect run success"

Arguably some of this is better now, but as d1bbbe45df8 did not
advocate for changing the output, let's revert this for now. It'll be
easy to change it back if that's what we'd prefer.

This does not change the one remaining use of "command.buf" to emit
the quoted argument, as that's new in d1bbbe45df8.

Some of these cases were not tested for in the tests added in the
preceding commit, I didn't have time to fleshen those out, but a look
at f1de981e8b6 will show that the other output being adjusted here is
now equivalent to what it was before d1bbbe45df8.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>