Use batch path deletion interface in vg paths -d

[glennhickey]

This PR updates libdsg/libhandlegraph to the latest versions. These include mutable_path_handlegraph::destroy_paths(). This is the equivalent of calling destroy_path() on each input item, except for PackedHandleGraph which implements its own faster version (vgteam/libbdsg#201).

But there's something wrong!

paths   version   time (s)
----------------------------
1       1.58      2.8
1       this      6.7
1       hash      12.6
11      1.58      11.3
11      this      49.2 
11      hash      14
111     1.58      97.8
111     this      479
111     hash      14.2

Command lines

packed graph for 1, 11, 111 paths (switch to 2.hg) for hash graph.

time vg paths -x /private/home/hickey/dev/work/slow-vg-clip -x 2.vg -Q simHuman_999 -d
time vg paths -x /private/home/hickey/dev/work/slow-vg-clip -x 2.vg -Q simHuman_99 -d
time vg paths -x /private/home/hickey/dev/work/slow-vg-clip -x 2.vg -Q simHuman_9 -d

[glennhickey]

For the record, this patch via 9429d62 seems to resolve the issue

packed graph deletion times with the patch are about 7 seconds across the board. Even doing 2500 paths (`-Q simHuman) is 40s which is in the same ballpark (30s) as hash graph. Thanks @jeizenga !