fix: fix invalid signature verification

[edisontim]

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?

Adapted the format of the signature to something more representative and fixed an issue with signatures not being verified correctly. Added some test cases that were generated by the javascript lib Noble

Does this introduce a breaking change?

• Yes
• No

Other information

[0xLucqs]

I have no clue what's happening here, can you add some context plz

[edisontim]

The format I was using before for the signature as well as for the public key was very inconvenient.
I also had a bug where I was verifying the r_sign and s_sign part of the signature in big-endian when they should've been in little-endian. In my tests this was working but using a signature generated from a standard library this wouldn't work out of the box, so changed that as well. Noticed it after @AbdelStark tried using this function.

[0xLucqs]

otherwise looks good