Implement AccountDatabaseReadableKVState

[IvanKavaldzhiev]

Problem

We should add AccountDatabaseReadableKVState, so that we can return accounts in PBJ format from DB.

Solution

Add AccountDatabaseReadableKVState in the following manner:

• Copy AccountDatabaseAccessor logic as a starting point
• Add repository queries for reading accounts from DB
• Add a new converter between entity and account DTO types to PBJ, so that the returned object is compliant with the hedera.app state

Alternatives

No response