Refactor: move Version to solidity-utils.

[jubeira]

Description

Moving Version to solidity utils (just a refactor).
We are already using it outside pools, and we'll use it for the relayer as well.

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Documentation or wording changes
• Other

Checklist:

• The diff is legible and has no extraneous changes
• N/A Complex code has been commented, including external interfaces
• N/A Tests are included for all code paths
• The base branch is either master, or there's a description of how to merge

Issue Resolution

N/A

[EndymionJkb]

Just one suggestion for the changelogs; otherwise LGTM.