Fix CacheListLengthResponse API

[rishtigupta]

CacheListLengthResponse API currently resolves to subtypes - Success and Error. It needs to resolve to subtypes Hit, Miss and Error according to SDK API Method Spec.

[rishtigupta]

Java SDK for example uses Hit, Miss, Error => https://github.com/momentohq/client-sdk-java/blob/main/momento-sdk/src/main/java/momento/sdk/messages/CacheListLengthResponse.java