[Prototype] Add partition-aware cache serializer

[pmaytak]

Related to #3285, #3439.

Adds a token cache serializer that accepts a cache partition key which allows to serialize only that specific partition and not the whole internal cache dictionary.

Example usage:

        public void BeforeAccessNotification(TokenCacheNotificationArgs args)
        {
            if (!string.IsNullOrEmpty(args.SuggestedCacheKey))
            {
                byte[] tokenCacheBytes = ReadCacheBytes(args.SuggestedCacheKey);
                ((IPartitionedTokenCacheSerializer)args.TokenCache).DeserializeMsal(tokenCacheBytes);
            }
        }

        public void AfterAccessNotification(TokenCacheNotificationArgs args)
        {
            if (args.HasStateChanged)
            {
                if (args.HasTokens)
                {
                    var key = string.IsNullOrEmpty(args.SuggestedCacheKey) ? args.Account.HomeAccountId.Identifier : args.SuggestedCacheKey;
                    WriteCacheBytes(key, ((IPartitionedTokenCacheSerializer)args.TokenCache).SerializeMsal(key));
                }
                else
                {
                    // No token in the cache. we can remove the cache entry
                    RemoveKey(args.SuggestedCacheKey);
                }
            }
        }