Currently, sparse_file_callback uses libsparse's
own logic for reading a file into a buffer. However,
a caller may want to use their own logic for doing
this in order to customize the buffer size and parallelize
the reads/writes. Also, a caller may want to implement
fill blocks with their own logic as well. To do this
add sparse_file_typed_callback which calls a different
callback function depending on the type of the sparse
chunk being written.
Test: Use typed callback for fd writes
Bug: 78793464
Change-Id: I75955a464fc05991f806339830fdfa05fda354b9
