Files TS: Convert file_table_list.js to TS

Fix 2 typing issues pointed by this conversion:
1. Add the `FilesAppEntry` to the accepted types in the MetadataModel.
Because it's common to send a random entry, that might be a
`FilesAppEntry` to MetadataModel.

2. Add `canPin` to `MetadataItem` which was missing.

Bug: b:289003444
Change-Id: I262c0a70b1a1a00324736e562ef3a7db7d159dc0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4987106
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Wenbo Jie <wenbojie@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1218008}