[Infobar Centralization] Add metrics tracking for the Centralized Infobar Framework

This CL implements sparse metrics tracking for the Centralized Infobar
Framework to evaluate the health, usage, and user engagement of desktop
infobars as they are migrated to the modern centralized manager.

Summary of changes:

Metrics Recording: Integrated sparse UMA tracking
(base::UmaHistogramSparse) using the InfoBarIdentifier. Show events are
logged in BrowserInfoBarManager when an infobar is successfully
displayed, while user interactions (Accept, Cancel, Dismiss, and
LinkClicked) are recorded in RegistryInfoBarDelegate.

Histogram Definitions: Registered the InfoBar.Centralized.{Action}
templated sparse metrics in browser/histograms.xml, describing the
bucket association with specific infobar identifiers.

Test Coverage: Added a CentralizedMetrics browser test case to
browser_infobar_manager_browsertest.cc using base::HistogramTester to
assert correct recording across all action types.

Bug: 523205725
Change-Id: Iac58d68304cd3e71a3b0a89a279943d67152d0d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8086963
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Darryl James <dljames@chromium.org>
Commit-Queue: Muhammad Salmaan <musalmaan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1661261}