Update last_used_time when the dictionary is used

This CL introduces UpdateDictionaryLastUsedTime method in
SQLitePersistentSharedDictionaryStore. The update operation is stored
in Backend::pending_last_used_time_updates_, and committed every 30
seconds or when called 100 times.

SharedDictionaryStorageOnDisk::GetDictionary() method calls this method
via SharedDictionaryManagerOnDisk to update the last_used_time in the
database.

Bug: 1413922
Change-Id: I824c175869fed48757eda587131b27cfdada3e20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4553982


Reviewed-by: Patrick Meenan <pmeenan@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1148285}