Draft: Etherlink/Kernel: static relative paths

What

This MR removes the /evm/world_state prefix from all path constants which have it. To avoid accidentally using relative paths instead of absolute ones or vice versa, a statically-checked distinction between relative and absolute paths is introduced.

Why

I assumed this was needed to support having multiple chains using distinct world states. In fact most of these paths are only used when accessing the world state through a safe storage and in this common particular case we can keep absolute paths (which are in fact relative to /tmp but this is abstracted away).

Still, this change set helps highlighting the rare cases where the world state is accessed (or even modified) without using a safe storage, which can be fragile.

How

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR