image_manager: set custom number of bytes to zero-fill

Add zeroFillNewImage function to the ImageService aidl interface.
Extend ZeroFillNewImage to allow the function caller to set the amount
of bytes that will be zero-filled in the given file.
This modification speeds up the process of initializing the CoW file
that will be used with a dm-snapshot device.

Change-Id: I242e57a9a622fbb738bf82f8a260af1b13810069
Bug: 139378014
Test: manual
Signed-off-by: Alessio Balsini <balsini@google.com>
5 files changed