[omnibox] Improve debug info for shortcuts in chrome://omnibox

1) When multiple shortcuts to the same stripped URL are deduped,
   chrome://omnibox currently displays 'number_of_hits' for 1 of the
   deduped shortcuts. With this CL, it'll instead show the sum of hits.
   This is more useful as it's what's used for scoring and because
   search shortcuts have many duplicates with 1 hit each because of SRP
   query params.

2) Likewise for 'last access time'; currently the time for 1 of the
   deduped shortcuts is shown. With this CL, the most recent time across
   the deduped shortcuts is shown.

3) This CL adds 'shortest shortcut text length' to the debug info.

No behavior change.

Bug: 327265991
Change-Id: I6a7637d7ebd26c244b74e6998748c274b1d6a246
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5332578
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Auto-Submit: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Orin Jaworski <orinj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1266724}