udev: modernize ctrl_send and use PROJECT_VERSION

udev: modernize ctrl_send and use PROJECT_VERSION

PROJECT_VERSION is used in preparation for future changes. Let's simplify the
code by using structured initialization. If the string written to .version ever
became to long, the compiler will truncate it and tell us:

../src/udev/udev-ctrl.c: In function ‘ctrl_send’:
../src/udev/udev-ctrl.c:221:28: warning: initializer-string for array of chars is too long
                 .version = "udev-" STRINGIFY(R_VERSION),
                            ^~~~~~~
../src/udev/udev-ctrl.c:221:28: note: (near initialization for ‘ctrl_msg_wire.version’)

No functional change.