Remove unnecessary listeners for the MiniMap

New class ToggleControl is used in place of the removed listeners.
Much cleaner code for the MiniMap chat rings.
Remove redundant debug setting: MiniMapChatRings.

-Thanks Liru for the advices.

indra/newview/app_settings/settings.xml

@@ -4788,7 +4788,7 @@ This should be as low as possible, but too low may break functionality</string>
       <key>Type</key>
       <string>U32</string>
       <key>Value</key>
-      <integer>8</integer>
+      <integer>32</integer>
     </map>
     <key>CurlTimeoutDNSLookup</key>
     <map>
@@ -10068,17 +10068,6 @@ This should be as low as possible, but too low may break functionality</string>
       <key>Value</key>
       <integer>1</integer>
     </map>
-    <key>MiniMapChatRings</key>
-    <map>
-      <key>Comment</key>
-      <string>Display chat distance rings on mini map</string>
-      <key>Persist</key>
-      <integer>1</integer>
-      <key>Type</key>
-      <string>Boolean</string>
-      <key>Value</key>
-      <integer>0</integer>
-    </map>
     <key>MiniMapWhisperRing</key>
     <map>
       <key>Comment</key>