sd-bus: escape invalid characters in error message

At many places, we pass arguments of dbus method calls to
sd_bus_error_setf(), and produces unprintable log messages.
Let's always escape the generated error message.

This fixes something like the following:
```
[ 1921.875668] systemd-logind[611]: Got message type=method_call sender=:1.46 destination=:1.6 path=/org/freedesktop/login1 interface=org.freedesktop.login1.Manager member=GetSeat  cookie=1344 reply_cookie=0 signature=s error-name=n/a error-message=n/a
[ 1921.875758] systemd-logind[611]: [725B blob data]
[ 1921.875777] systemd-logind[611]: [768B blob data]
```

src/libsystemd/sd-bus/bus-error.c

@@ -7,6 +7,7 @@
 #include "errno-list.h"
 #include "errno-util.h"
 #include "string-util.h"
+#include "utf8.h"
 
 BUS_ERROR_MAP_ELF_REGISTER const sd_bus_error_map bus_standard_errors[] = {
         SD_BUS_ERROR_MAP(SD_BUS_ERROR_FAILED,                             EACCES),
@@ -246,7 +247,7 @@ _public_ int sd_bus_error_setfv(sd_bus_error *e, const char *name, const char *f
                          * this, since we at least managed to write the error name */
 
                         if (vasprintf(&mesg, format, ap) >= 0)
-                                e->message = TAKE_PTR(mesg);
+                                e->message = utf8_escape_non_printable(mesg);
                 }
 
                 e->_need_free = 1;