[FilesRecentFilter] Support clearing cache for getRecentFiles

* Add a new "invalidateCache" parameter to the private extension API
chrome.fileManagerPrivate.getRecentFiles() so we can explicitly clear
the recent file query cache in the backend.
* Add a new "invalidateCache" parameter to DirectoryModel.rescan() so
it can be passed down to chrome.fileManagerPrivate.getRecentFiles().
* This is useful for when we try to refetch the recent file list right
after deletion. Without this the recent file list will still show the
deleted file if the deletion happens within 10s from the last fetch.

Bug: 1324048
Change-Id: I24bd62c4c3ffefbe35cf3af9e7860a49d48dd9ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3653375
Reviewed-by: Glen Robertson <glenrob@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Wenbo Jie <wenbojie@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1006333}