system_queries: Migrate system queries into a single place

This provides better separation of the DBus interface and the underlying
system interactions.

Change-Id: I8bf7a44c679ab065f959af19a00c29897c1d5c48
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/meson.build b/src/meson.build
index 84c2f82..184eb4a 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -54,6 +54,7 @@
   'network_config.cpp',
   'network_manager.cpp',
   'system_configuration.cpp',
+  'system_queries.cpp',
   'util.cpp',
   'routing_table.cpp',
   'config_parser.cpp',