add: update --renormalize to skip sparse paths

add: update --renormalize to skip sparse paths

We added checks for path_in_sparse_checkout() to portions of 'git add'
that add warnings and prevent stagins a modification, but we skipped the
--renormalize mode. Update renormalize_tracked_files() to ignore cache
entries whose path is outside of the sparse-checkout cone (unless
--sparse is provided). Add a test in t3705.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>