configure: build sulogin, watchdogd, and libsystemd by default

v5.0 ships keventd and the D-Bus support enabled out of the box, but the
remaining bundled pieces stayed opt-in, and the help text for two of them
already claimed otherwise.

Default all three to yes; --without-sulogin, --without-watchdog, and
--without-libsystemd opt out.  The distcheck and CI configure lines drop
the flags they no longer need, so CI exercises the defaults.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

.github/workflows/release.yml

@@ -46,8 +46,7 @@ jobs:
           ./autogen.sh
           ./configure  --prefix=/usr --exec-prefix= --sysconfdir=/etc  \
                        --localstatedir=/var --enable-x11-common-plugin \
-                       --enable-testserv-plugin --with-watchdog        \
-                       --with-keventd --with-libsystemd
+                       --enable-testserv-plugin
       - name: Enable unprivileged userns (unshare)
         run: |
           sudo sysctl kernel.apparmor_restrict_unprivileged_userns=0