evm/kernel: read first element from the linked list

Context

Under the hood, the delayed inbox will use a linked list as described in this document: https://docs.google.com/document/d/1u5U1_nQnrsJGDGBRV6w-U7Pf8uXPzu-tD3-AUErSJig/edit#heading=h.hwvonqcrff4o

The goal of the linked list is to provide basic primitive over the linked list:

• empty/constuctor: to create a linked list !11107 (merged)
• push: to push an element at the end of the list !11108 (merged)
• get: to retrieve an element from the list !11108 (merged)
• remove: to remove an element at any position of the list !11109 (merged)
• front: to retrieve the first element of the list !11110 (merged)
• pop: to remove the first element of the list !11111 (merged)

This MR represents the read first element primitive of the linked list.

Manually testing the MR

cd src/kernel_evm && make build && make check && make test

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