refactor(e2store): refactor e2store utils

[ogenev]

What was wrong?

Converting bytes to rust types and rust types to bytes is common as serializing and deserializing.
Even if we don't use the serde framework for deserializing/serializing Era files (at this stage), I think it is nice if we don't deviate much from the common concepts.

How was it fixed?

• rename File to E2storeFIle
• Reading from a byte slice is confusing with reading into a buffer which is typical to Readers. To remove this confusion, I renamed read to deserialize because this is what we are trying to do here: deserialize from a byte slice into a type.
• To keep consistent with the above, I renamed encode to serialize.

• Clean up commit history and use conventional commits.

[njgheorghita]

🚢