util-lib: move formats-util.h from shared/ to basic/

It's only a header file, definining format strings for basic system
types, hence it should be in src/basic/, not src/shared/.

diff --git a/src/shared/formats-util.h b/src/basic/formats-util.h
similarity index 100%
rename from src/shared/formats-util.h
rename to src/basic/formats-util.h