[omnibox] Optimize MostVisitedProvider matches creation.

This does 3 things in order to optimize the creation of MostVisited
matches.
1) Limits the amount of results requested from history to 500.
2) Limit the # of open tabs we compare with to 500.
3) Stop iterating through history URLs if a sufficient amount of matches
have been created. There's no need to keep making additional matches.

The only drawback from 2 (which should be super rare) is if all 500
results requested from history are equivalent to the first 500 open
tabs, then no results will be shown.

Change-Id: I28b4cf47c51f57aac4d9f161d966e0d7875c9b4d
Bug: 417304130
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6579533
Commit-Queue: Nihar Majmudar <niharm@google.com>
Reviewed-by: Orin Jaworski <orinj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1468244}