shared: move wait-online's dns-configuration.[ch] to shared

src/network/meson.build

@@ -116,7 +116,6 @@ systemd_networkd_extract_sources = files(
 )
 
 systemd_networkd_wait_online_sources = files(
-        'wait-online/dns-configuration.c',
         'wait-online/wait-online-link.c',
         'wait-online/wait-online-manager.c',
         'wait-online/wait-online.c',

src/shared/meson.build

@@ -61,6 +61,7 @@ shared_sources = files(
         'dissect-image.c',
         'dm-util.c',
         'dns-answer.c',
+        'dns-configuration.c',
         'dns-domain.c',
         'dns-packet.c',
         'dns-question.c',