Added commands: !handles, !jo_prev, !jo_next, !jo_in_range, !jot, !dp.

Command descriptions:
  !handles: print stats for handles or list them;
  !jo_prev, !jo_next, !jo_in_ range: print managed objects near the given address;
  !jo_in_range: print managed objects in the given range;
  !jot: print the tree of referenced objects, starting from a given root;
  !dp: 'dp'-like command, augmented with data about the managed pointers.

Change-Id: Ic72dd52ee8c68bc559f37ae04870d4e63ae0d554
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1772694
Commit-Queue: Irina Yatsenko <irinayat@microsoft.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63435}