SOURCE_COPY operation: implement src == dst

Helper function to compare the source and destination extents of a
SOURCE_COPY InstallOperation.
The function returns true iff source and destination are identical with
the use of std::equal().

Bug: 141207436
Test: build
Change-Id: I146aeba1c8ede35f21cfef8e21d4af62274bda84
Signed-off-by: Alessio Balsini <balsini@google.com>