Instead of truncating iovecs when len(iovecs) > MaxReadWriteIov, we should
attempt a full write. There are multiple users of hostfd:
- tmpfs (when using file backend)
- gofer client
- hostinet
- fsimpl/host
These callers use hostfd to implement all read/write operations. Even though
read/write syscall semantics allow for short IO, Linux seems to be doing full
reads/writes. For compatibility, hostfd should attempt full IO.
PiperOrigin-RevId: 582050290