[lib][libc-trusty] Implement read{v} and write{v} routines

This CL adds an implementation of read/readv and write/writev
routines as wrappers over underlying _trusty_readv and
_trusty_writev syscalls. These routines can be invoked on fds
or handles that supports such operations and should behave
similar to standard libc read/write{v} routines.

Bug: 149059166
Change-Id: I6ff560a6b2808b15a55b556e18dbee83479a1547
5 files changed