[FilesTrash] Add skeleton RestoreIOTask

This implements a skeleton RestoreIOTask and ensure it builds. This task
represents restoring a file that has previously been trashed. Upcoming
CLs will implement the details ensuring to follow the XDG specification.

Bug: b:231830250
Test: Ensure chrome builds
Test: unit_tests --gtest_filter=*IOTaskTest*
Change-Id: I4c25b129e26cee7f492bb56ac012f4d226a373b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3676599
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Ben Reich <benreich@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1009564}