Got rid of cancellation signals in the Content Capture Data Sharing

Motivation: if the Content Capture service want's to end the session, it
can close the read-fd, while not have finished reading, and that would
result in an exception in the system server, that can later be
propagated to the caller as an error.

Similarly, timeout of the sharing session can be reflected as an error
with a specific error code.

Test: built Android locally and perfomed a manual test.
Bug: 145203958
Change-Id: Iaeb45e0ab68da9fe30dce1ae4eab2354ef56d827