libfsosystem: import write method from libfsobasics
libfsosystem: import write method from libfsobasics

There is currently no clear line between libfsobasics and libfsosystem so we need to
define what should be in which one and migrate all dependencies to use the the correct
library.

Signed-off-by: Simon Busch <e923d8431f09840b119134ca71ec8d74989d15cc@gravedo.de>

slyon/debian-fso-deviced,slyon/debian-fso-usaged,slyon/debian-fso-usaged,slyon/debian-fso-deviced