feat: Little endian support for ByteArray extensions

[sveamarcus]

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?

• Currently supports encoding and decoding from big endian ByteArray, which remains the default behaviour.

What is the new behavior?

• Adds support for little endian encoding when storing or reading a ByteArray

Does this introduce a breaking change?

• Yes
• No

Other information

[sveamarcus]

There is an update coming to ByteArrayReader as well. Then, there is a pending addition of SipHash optimized for cairo/validity proofs, which depends on these little endian additions.