Remove limitation on read/write size

Previously ios called through read write
were limited to 16kb because read packets
are very small. However, write packets can
be greater than that amount in cases where
a folder contains over 4k items. Thus,
remove the limitation.

Add corresponding ReadLarge and WriteLarge
tests as well.

Bug: 79214960
Test: mtp_ffs_handle_test passes, Mtp works
with large folders

Change-Id: I8a980612c3eb941552ff4dd11ac631d1dc5d3347