copy: change the various copy_xyz() calls to take a unified flags parameter

This adds a unified "copy_flags" parameter to all copy_xyz() function
calls, replacing the various boolean flags so far used. This should make
many invocations more readable as it is clear what behaviour is
precisely requested. This also prepares ground for adding support for
more modes later on.

src/systemctl/systemctl.c

@@ -5300,7 +5300,7 @@ static int cat_file(const char *filename, bool newline) {
                ansi_normal());
         fflush(stdout);
 
-        return copy_bytes(fd, STDOUT_FILENO, (uint64_t) -1, false);
+        return copy_bytes(fd, STDOUT_FILENO, (uint64_t) -1, 0);
 }
 
 static int cat(int argc, char *argv[], void *userdata) {
@@ -6582,7 +6582,7 @@ static int create_edit_temp_file(const char *new_path, const char *original_path
         if (r < 0)
                 return log_error_errno(r, "Failed to create directories for \"%s\": %m", new_path);
 
-        r = copy_file(original_path, t, 0, 0644, 0);
+        r = copy_file(original_path, t, 0, 0644, 0, COPY_REFLINK);
         if (r == -ENOENT) {
 
                 r = touch(t);