[NDM] [Cisco ACI] Refactor fabric test

[zoedt]

What does this PR do?

Refactoring the tests for Cisco ACI fabric, first iteration towards an easier testing/dev experience (for this PR #18747)

Summary of changes made

• Reduce number of devices/interfaces to be more manageable
• Update test fixtures accordingly
• Organize metric assertions into group

Motivation

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.68%. Comparing base (50589cb) to head (acc0399).

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
cisco_aci	89.37% <ø> (-5.68%)	⬇️
hive	?
hivemq	?
ignite	?
jboss_wildfly	?
kafka	?
presto	?
solr	?

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