Rework caching

This does a *lot* of things. Essentially, it replaces the existing
individual proxy- and autoproxy caches on the bot end with a
global cache (in Core) that handles all the caching at once, and
automatically invalidates the cache once something changes in the
datastore.

This allows us to do proxying and autoproxying with *zero database
queries* (best-case).

PluralKit.Bot/Commands/MemberProxy.cs

@@ -8,12 +8,10 @@ namespace PluralKit.Bot.Commands
     public class MemberProxy
     {
         private IDataStore _data;
-        private ProxyCacheService _proxyCache;
         
-        public MemberProxy(IDataStore data, ProxyCacheService proxyCache)
+        public MemberProxy(IDataStore data)
         {
             _data = data;
-            _proxyCache = proxyCache;
         }
 
         public async Task Proxy(Context ctx, PKMember target)
@@ -117,9 +115,6 @@ namespace PluralKit.Bot.Commands
                 await _data.SaveMember(target);
                 await ctx.Reply($"{Emojis.Success} Member proxy tags set to `{requestedTag.ProxyString.SanitizeMentions()}`.");
             }
-
-            await _proxyCache.InvalidateResultsForSystem(ctx.System);
         }
-
     }
 }