Fix(eos_designs): Fix context vars for custom interface description templates

[ClausHolbechArista]

Change Summary

Fix context vars for custom interface description templates

Related Issue(s)

Fixes #4428

Component(s) name

arista.avd.eos_designs

Proposed changes

• Fixing various missing context variables.
• Adding all available context variables to documentation

How to test

• Updated molecule.

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)

[github-actions]

Review docs on Read the Docs

To test this pull request:

# Create virtual environment for this testing below the current directory
python -m venv test-avd-pr-4437
# Activate the virtual environment
source test-avd-pr-4437/bin/activate
# Install all requirements including PyAVD
pip install "pyavd[ansible] @ git+https://github.com/ClausHolbechArista/avd.git@cherry-pick-4429#subdirectory=python-avd" --force
# Point Ansible collections path to the Python virtual environment
export ANSIBLE_COLLECTIONS_PATH=$VIRTUAL_ENV/ansible_collections
# Install Ansible collection
ansible-galaxy collection install git+https://github.com/ClausHolbechArista/avd.git#/ansible_collections/arista/avd/,cherry-pick-4429 --force
# Optional: Install AVD examples
cd test-avd-pr-4437
ansible-playbook arista.avd.install_examples

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[carlbuchmann]

LGTM