test: add atm e2e tests

[zhiying-lin]

What type of PR is this?
/kind test

What this PR does / why we need it:
Add first negative e2e tests for ATM.

Which issue(s) this PR fixes:

Fixes #

Requirements:

• run make reviewable for basic local test
• Read and followed fleet-networking's Code of conduct.
• uses conventional commit messages
• includes documentation
• adds unit tests

How has this code been tested

https://github.com/Azure/fleet-networking/actions/runs/12296154911/job/34314583519 test passed

Special notes for your reviewer

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.05%. Comparing base (c4356a7) to head (f5477bb).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #231      +/-   ##
==========================================
+ Coverage   79.76%   80.05%   +0.28%     
==========================================
  Files          27       27              
  Lines        3840     3840              
==========================================
+ Hits         3063     3074      +11     
+ Misses        621      611      -10     
+ Partials      156      155       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jwtty]

In general, lgtm. But I think we should also setup an Azure client and check the ATM Azure source status.

[zhiying-lin]

In general, lgtm. But I think we should also setup an Azure client and check the ATM Azure source status.

Before, i was thinking of the e2e should not tightly depend on our implementation, eg, how to get this actual azure resource. But since the validation cannot be done in the integration test, i will add the azure validation in a separate PR in case of the regression.