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/libsystemd/sd-bus/test-bus-watch-bind.c

@@ -8,7 +8,6 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
-#include "fileio.h"
 #include "fs-util.h"
 #include "mkdir.h"
 #include "path-util.h"
@@ -16,6 +15,7 @@
 #include "rm-rf.h"
 #include "socket-util.h"
 #include "string-util.h"
+#include "tmpfile-util.h"
 
 static int method_foobar(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
         log_info("Got Foobar() call.");

src/libsystemd/sd-device/device-private.c

@@ -24,6 +24,7 @@
 #include "string-util.h"
 #include "strv.h"
 #include "strxcpyx.h"
+#include "tmpfile-util.h"
 #include "user-util.h"
 #include "util.h"
 

src/libsystemd/sd-event/test-event.c

@@ -6,7 +6,6 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
-#include "fileio.h"
 #include "fs-util.h"
 #include "log.h"
 #include "macro.h"
@@ -17,6 +16,7 @@
 #include "stdio-util.h"
 #include "string-util.h"
 #include "tests.h"
+#include "tmpfile-util.h"
 #include "util.h"
 
 static int prepare_handler(sd_event_source *s, void *userdata) {

src/libsystemd/sd-hwdb/hwdb-util.c

@@ -16,6 +16,7 @@
 #include "strbuf.h"
 #include "string-util.h"
 #include "strv.h"
+#include "tmpfile-util.h"
 
 static const char *default_hwdb_bin_dir = "/etc/udev";
 static const char * const conf_file_dirs[] = {