[MVT] Visual Deduplication of MVT

Once the MVT algorithm has scored and ordered URL segments,
we filter them further by matching HostName AND title (First N characters).

if any 2 URLs match, then the URL with the higher score is kept, and the other skipped.

Reason for the Match condition:
- URLs with similar hostnames would likely share the same favicon.
- titles longer than 10 get truncated to 10.
- MVT that share both of these would likely be indistinguishable.

Bug: 417414647
Change-Id: Icb8add96e617b43f96cd4681fb8eed75b5fb5663
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6548335
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Auto-Submit: Hitarth Kothari <hitarthkothari@google.com>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1469269}