fix(map): Streamline behaviour for the ttt2_enable_map_prefix_ convars

* Unconditionally create gm, ttt and ttt2 prefixes

We can reasonably assume `gm` maps to be present on the server, the same
goes for `ttt` and `ttt2` maps.
Even if either or both of them are not currently installed on the server
creating these unconditionally would allow an admin to configure their
behaviour in that case.

Creating convars dynamically if we find more map prefixes is still
done.

* Disable all map prefixes but `ttt` and `ttt2` by default

We will assume people only want to run maps intended for ttt(2).

Given that the prefix selection can be modified on the same admin
settings page that is (currently) the only one using these convars this
seems fine.

* Drop FCVAR_NOTIFY for all `map_prefix_enabled` convars

Given that these are purely used in an admin context there is no need to
announce changes to all users on the server.

The last changes especially fixes the original Issue #1632

lua/ttt2/libraries/map.lua

@@ -502,19 +502,32 @@ local mapsPrefixes = {}
 local mapsWSIDs = {}
 
 if SERVER then
-    -- by default cs, de and test maps should be hidden
+    -- by default cs, de, gm and test maps should be hidden
+    -- while ttt and ttt2 maps should be shown
 
     ---
     -- @realm server
-    CreateConVar("ttt2_enable_map_prefix_cs", "0", { FCVAR_ARCHIVE, FCVAR_NOTIFY })
+    CreateConVar("ttt2_enable_map_prefix_cs", "0", { FCVAR_ARCHIVE })
 
     ---
     -- @realm server
-    CreateConVar("ttt2_enable_map_prefix_de", "0", { FCVAR_ARCHIVE, FCVAR_NOTIFY })
+    CreateConVar("ttt2_enable_map_prefix_de", "0", { FCVAR_ARCHIVE })
 
     ---
     -- @realm server
-    CreateConVar("ttt2_enable_map_prefix_test", "0", { FCVAR_ARCHIVE, FCVAR_NOTIFY })
+    CreateConVar("ttt2_enable_map_prefix_gm", "0", { FCVAR_ARCHIVE })
+
+    ---
+    -- @realm server
+    CreateConVar("ttt2_enable_map_prefix_test", "0", { FCVAR_ARCHIVE })
+
+    ---
+    -- @realm server
+    CreateConVar("ttt2_enable_map_prefix_ttt", "1", { FCVAR_ARCHIVE })
+
+    ---
+    -- @realm server
+    CreateConVar("ttt2_enable_map_prefix_ttt2", "1", { FCVAR_ARCHIVE })
 
     ---
     -- Initializes the map list. Searches the file system for available maps, scans those maps
@@ -570,7 +583,7 @@ if SERVER then
 
             ---
             -- @realm server
-            CreateConVar(convarName, "1", { FCVAR_ARCHIVE, FCVAR_NOTIFY })
+            CreateConVar(convarName, "0", { FCVAR_ARCHIVE })
 
             -- because these convars are generated dynamically, replicated convars do not work here
             SetGlobalBool(convarName, GetConVar(convarName):GetBool())