Feat(eos_designs): Add optional cv-pathfinder site for pathfinders

[ClausHolbechArista]

Change Summary

Add optional cv-pathfinder site for pathfinders

Component(s) name

arista.avd.eos_designs

Proposed changes

# Define sites that are outside of the CV Pathfinder hierarchy.
# This is used to arrange pathfinders in the CloudVision topology layout.
cv_pathfinder_global_sites:     <------- NEW

  # The site name.
  - name: <str; required; unique>
    description: <str>

    # Location as a string is resolved on Cloudvision.
    location: <str>

<node-type-key>:
  defaults:
    # The CV Pathfinder region name.
    # This key is required for WAN routers but optional for pathfinders.
    # The region name must be defined under 'cv_pathfinder_regions'.
    cv_pathfinder_region: <str>

    # The CV Pathfinder site name.
    # This key is required for WAN routers but optional for pathfinders.
    # For WAN routers and pathfinders with `cv_pathfinder_region`, the site name must be defined for the relevant region under 'cv_pathfinder_regions'.
    # For pathfinders without `cv_pathfinder_region` set, the site must be defined under `cv_pathfinder_global_sites`.
    cv_pathfinder_site: <str>     <------- MODIFIED BEHAVIOR (SEE DESCRIPTION)

How to test

Updated molecule to have all combinations of region, region+site, site

Checklist

User Checklist

• N/A

Repository Checklist

• My code has been rebased from devel before I start
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation and documentation have been updated accordingly.
• I have updated molecule CI testing accordingly. (check the box if not applicable)