commit-graph.c: pass progress to `verify_one_commit_graph()`

commit-graph.c: pass progress to `verify_one_commit_graph()`

This is the final step to prepare for consolidating the output of `git
commit-graph verify`. Instead of having each call to
`verify_one_commit_graph()` initialize its own progress struct, have the
caller pass one in instead.

This patch does not alter the output of `git commit-graph verify`, but
the next commit will consolidate the output.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>