feat: Implement RLP Encoding and Decoding

[Quentash]

Implementation of RLP encoding and decoding based on https://ethereum.org/en/developers/docs/data-structures-and-encoding/rlp/ doc.

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: #212

What is the new behavior?

Does this introduce a breaking change?

• Yes
• No

Other information

[0xLucqs]

Same for other functiosn

[Quentash]

Created a errors.cairo file inside encoding crate.
Changed panics to Results.

[Quentash]

• Simplified errors handling and therefore deleted errors.cairo.
• Moved RLPError into rlp.cairo
• Made a generic trait but not sure about the name, do you have any suggestion ?
• Added tests for the U32Impl in integers.cairo
• Corrected list encoding tests variables naming
• Added comments to explain the safe unwraps.

[0xLucqs]

remove the unnecessary (()) and either remove the unwraps or say why they're safe plz

[Quentash]

• Modified error handling for PayloadTooLong using ok_or() instead of the unsafe unwrap()

[Quentash]

• Moved comments right above their appropriate unwrap()
• Removed once and for all the (()) ( my very bad )