git reflog [expire|delete]: make -h output consistent with SYNOPSIS

git reflog [expire|delete]: make -h output consistent with SYNOPSIS

Make use of the guaranteed pretty alignment of "-h" output added in my
4631cfc20bd (parse-options: properly align continued usage output,
2021-09-21) and wrap and format the "git reflog [expire|delete] -h"
usage output. Also add the missing "--single-worktree" option, as well
as adding other things that were in the SYNOPSIS output, but not in
the "-h" output.

This was last touched in 33d7bdd6459 (builtin/reflog.c: use
parse-options api for expire, delete subcommands, 2022-01-06), but in
that commit the previous usage() output was faithfully
reproduced. Let's follow-up on that and make this even easier to read.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>