test: garbage collection controller removes orphaned nics

[Bryce-Soghigian]

Description
This pr adds an e2e test that can be ran locally for network interface garbage collection.

How was this change tested?

• make az-e2etests on byo vnet + managed vnet
• E2E Run

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

Release Note

[charliedmcb]

Overall, looks pretty good. Good to get the test coverage.

Main points looking to have addressed are test timeout, and comments clarifying magic indexes.

[Bryce-Soghigian]

Passing E2E Run: https://github.com/Azure/karpenter-provider-azure/actions/runs/13253672683/job/36996595816

[tallaxes]

(Have not finished the review, capturing feedback so far - probably already actionable. Overall like where this is going!)

[tallaxes]

Very close

[Bryce-Soghigian]

Running e2e suite with changes to imports: https://github.com/Azure/karpenter-provider-azure/actions/runs/13386002889, lets see if it works as expected.