boca: Add a delegate to provide load time data.

This is needed as we won't have a easy way to access user pref after we
changed from feature flag to policy check. This is also needed to
provide more load time data in /chrome to boca app. Also add locale into
load time data.

Bug: b:373484445

Change-Id: Ib8854deac603f6b81742cb1a6a5ceef4879232b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5941424
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: April Zhou <aprilzhou@google.com>
Reviewed-by: Benjamin Zielinski <bzielinski@google.com>
Cr-Commit-Position: refs/heads/main@{#1372234}