feat(anta.tests): Add testcases for ISIS SR Adjascency Segments

[titom73]

Description

Implement testcases related to ISIS-SR environment

• Check Adjacency segments
• Check ISIS-SR dataplane
• Check for tunnels computed by device
• Presence of a tunnel with specific endpoint
  • Optionally, Check its interface
  • Optionally, Check its nexthop
  • Optionally, Check its tunnel type
  • Optionally, Check if it is tunnel, then it is TI-LFA

All unit tests are created.

Fixes #636

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have run pre-commit for code linting and typing (pre-commit run)
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes (tox -e testenv)

[titom73]

Waiting for PR #691 to be merged first for pre-commit stuff