Review, organize, and refactor the public methods of the AbstractStorage implementations

## Motivation

- We want to avoid having implementation-specific public methods whenever possible.
Therefore, let’s review all public methods, list which ones have a clear justification for existing, and remove any methods that are unnecessary.

## Details

- Let’s list all public methods that are currently in use.
- Let’s document the rationale for why each public method should exist, or at least note it in comments.
- Let’s remove any public methods that are unnecessary.

JIRA Issue: BA-3797