coral: get in-session file name (1/2)

To provide more useful information, we need to get file name from the
reader app. For SWAs and PWAs, the file names can be gotten from the
tab title. Therefore, we get tab, SWA, and PWA from TabClusterUIItem
and use the tab title as the file name.

The tab title will be written to app info after the file name field
is added to the app mojom struct.

Bug: b:383895688
Change-Id: Id7f4b14c45e6f2d95d74ac86f4744e133b0bc25a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6102592
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Xiaodan Zhu <zxdan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1398371}