…ltiple times

Reuse extent-cache facility to record multiple bytenr so '-b|--block'
can be specified multiple times.

Despite that, add a sector size alignment check before we try to print a
tree block.
(Please note that, nodesize alignment check is not suitable here as meta
chunk start bytenr could be unaligned to nodesize)

Signed-off-by: Qu Wenruo <wqu@suse.com>