Implementation of rlp::decode()

[Quentash]

Implementation of rlp::decode() as it was benchmarked and tested here (https://github.com/danilowhk/cairo-lib/blob/main/src/encoding/rlp.cairo).

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?

Resolves: #

What is the new behavior?

Does this introduce a breaking change?

• Yes
• No

[Quentash]

I clearly misunderstood the assignment that I have been given. I indeed thought that I was asked to implement the whole eth_transaction.cairo file by using the rlp.cairo fork linked above as an external import.
As far as I understand now, I was asked to import the rlp.cairo file into kakarot source files. Which I therefore quickly did.
I've left what I experimented in eth_transaction.cairo because it was using what I think to be a good example ( taken from here : https://eips.ethereum.org/EIPS/eip-155 ) and somehow also tests the rlp::decode() utils in a more "concrete" way.

I am terribly sorry if whatever I have done here is completly out of scope! I'm well aware some code will need to be removed but pushing now allow me to clarify this confusion with you guys so I can finish what I have been asked!

[Eikix]

The scope of this PR is too large. Could you break it down into two PRs, one for the RLP trait & RLP decode
And the second one for the EOA logic: decode_tx?

[enitrat]

almos lgtm now wdyt @Eikix

[Eikix]

almos lgtm now wdyt @Eikix

agreed

[enitrat]

lgtm, proposed variable name changes to make it easier to understand on first read.

[enitrat]

LGTM