track CLS compliance; KeyDeleteAsync should have been using UNLINK sometimes; make RCS happier

src/StackExchange.Redis/AssemblyInfoHack.cs

 // Yes, this is embarassing. However, in .NET Core the including AssemblyInfo (ifdef'd or not) will screw with
 // your version numbers. Therefore, we need to move the attribute out into another file...this file.
 // When .csproj merges in, this should be able to return to Properties/AssemblyInfo.cs
+using System;
 using System.Runtime.CompilerServices;
 [assembly: InternalsVisibleTo("StackExchange.Redis.Server, PublicKey=00240000048000009400000006020000002400005253413100040000010001007791a689e9d8950b44a9a8886baad2ea180e7a8a854f158c9b98345ca5009cdd2362c84f368f1c3658c132b3c0f74e44ff16aeb2e5b353b6e0fe02f923a050470caeac2bde47a2238a9c7125ed7dab14f486a5a64558df96640933b9f2b6db188fc4a820f96dce963b662fa8864adbff38e5b4542343f162ecdc6dad16912fff")]
 [assembly: InternalsVisibleTo("StackExchange.Redis.Tests, PublicKey=00240000048000009400000006020000002400005253413100040000010001007791a689e9d8950b44a9a8886baad2ea180e7a8a854f158c9b98345ca5009cdd2362c84f368f1c3658c132b3c0f74e44ff16aeb2e5b353b6e0fe02f923a050470caeac2bde47a2238a9c7125ed7dab14f486a5a64558df96640933b9f2b6db188fc4a820f96dce963b662fa8864adbff38e5b4542343f162ecdc6dad16912fff")]
 [assembly: InternalsVisibleTo("NRediSearch.Test, PublicKey=00240000048000009400000006020000002400005253413100040000010001007791a689e9d8950b44a9a8886baad2ea180e7a8a854f158c9b98345ca5009cdd2362c84f368f1c3658c132b3c0f74e44ff16aeb2e5b353b6e0fe02f923a050470caeac2bde47a2238a9c7125ed7dab14f486a5a64558df96640933b9f2b6db188fc4a820f96dce963b662fa8864adbff38e5b4542343f162ecdc6dad16912fff")]
+
+[assembly: CLSCompliant(true)]

src/StackExchange.Redis/RedisDatabase.cs

@@ -605,7 +605,7 @@ public long KeyDelete(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
         public Task<bool> KeyDeleteAsync(RedisKey key, CommandFlags flags = CommandFlags.None)
         {
             var cmd = GetDeleteCommand(key, flags, out var server);
-            var msg = Message.Create(Database, flags, RedisCommand.DEL, key);
+            var msg = Message.Create(Database, flags, cmd, key);
             return ExecuteAsync(msg, ResultProcessor.DemandZeroOrOne, server);
         }
 
@@ -3770,10 +3770,7 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
                     case ResultType.SimpleString:
                     case ResultType.BulkString:
                         RedisValue value = result.AsRedisValue();
-                        var sgwem = message as StringGetWithExpiryMessage;
-                        TimeSpan? expiry;
-                        Exception ex;
-                        if (sgwem != null && sgwem.UnwrapValue(out expiry, out ex))
+                        if (message is StringGetWithExpiryMessage sgwem && sgwem.UnwrapValue(out var expiry, out var ex))
                         {
                             if (ex == null)
                             {