cros: Add RequestCopyFileFromLocal to MTP client

Replace `CopyFileFromLocal` with `RequestCopyFileFromLocal`.
The new dbus API returns after the file copying request is
scheduled. The copy result is emitted by MTP daemon as
a new `CopyFileFromLocalCompleted` dbus signal.

Bug: b:388332345
Change-Id: Ia624639aa24f28e4bd6f2359e0cf2daa7c32e557
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6251797
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: François Degros <fdegros@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1421971}