[CBRD-22389] Improves access at class representation

[alexstanro]

Avoids mutex acquisition of cache representation, as much as possible. Keeps cache fix count, version and decache flag into a 64 bytes value. Also, keeps reference to the class representation entry, version at last access of the cache entry, transaction fix count and pin. All these information are used to detect when the class representation cache has changed, was fixed, pinned. Based on this values, the transaction can decide whether it needs cache mutex acquisition or not.