refactor: split up database/key_value.rs

src/database/key_value/mod.rs

@@ -0,0 +1,13 @@
+mod account_data;
+mod admin;
+mod appservice;
+mod globals;
+mod key_backups;
+mod media;
+mod pdu;
+mod pusher;
+mod rooms;
+mod sending;
+mod transaction_ids;
+mod uiaa;
+mod users;