util-lib: split out all temporary file related calls into tmpfiles-util.c

This splits out a bunch of functions from fileio.c that have to do with
temporary files. Simply to make the header files a bit shorter, and to
group things more nicely.

No code changes, just some rearranging of source files.

src/machine/machine-dbus.c

@@ -34,6 +34,7 @@
 #include "signal-util.h"
 #include "strv.h"
 #include "terminal-util.h"
+#include "tmpfile-util.h"
 #include "user-util.h"
 
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_class, machine_class, MachineClass);

src/machine/machine.c

@@ -26,6 +26,7 @@
 #include "stdio-util.h"
 #include "string-table.h"
 #include "terminal-util.h"
+#include "tmpfile-util.h"
 #include "unit-name.h"
 #include "user-util.h"
 #include "util.h"

src/machine/machined-dbus.c

@@ -25,6 +25,7 @@
 #include "process-util.h"
 #include "stdio-util.h"
 #include "strv.h"
+#include "tmpfile-util.h"
 #include "unit-name.h"
 #include "user-util.h"