mkfs-util: turn quiet/discard to a flags field

Add a new `MakeFilesystemFlags` enum and use it to replace the existing
`quiet` and `discard` booleans on `make_filesystem()`.

Update the callers.  While we're doing that, consolidate some duplicated
logic in systemd-repart.

Signed-off-by: Allison Karlitskaya <allison.karlitskaya@redhat.com>

src/growfs/makefs.c

@@ -70,8 +70,7 @@ static int run(int argc, char *argv[]) {
                                label,
                                /* root = */ NULL,
                                uuid,
-                               /* discard = */ true,
-                               /* quiet = */ true,
+                               MKFS_DISCARD | MKFS_QUIET,
                                /* sector_size = */ 0,
                                /* compression = */ NULL,
                                /* compression_level = */ NULL,