[Weighted Shard Routing] Revisit weighted routing cache

[anshu1106]

Describe the solution you'd like
Revisit WeightedRoutingCache and see if we can make it more optimal. Currently the cache is invalidated on every cluster state change which is not needed and can affect performance.

• Check if we can leverage AttributeRoutings which is invalidated only on change in shard routing.

 static class AttributesRoutings {

        public final List<ShardRouting> withSameAttribute;
        public final List<ShardRouting> withoutSameAttribute;
        public final int totalSize;

        AttributesRoutings(List<ShardRouting> withSameAttribute, List<ShardRouting> withoutSameAttribute) {
            this.withSameAttribute = withSameAttribute;
            this.withoutSameAttribute = withoutSameAttribute;
            this.totalSize = withoutSameAttribute.size() + withSameAttribute.size();
        }
    }

• Make WeightedRoutingCache more performant.

[anshu1106]

#4241 (comment)
#4241 (comment)

[anshu1106]

Closing this issue. This is fixed in 4241