Add TestVMWithStorageNetwork

[albinsun]

Which issue(s) this PR fixes:

Issue #1022 for harvester/harvester#4886

What this PR does / why we need it:

1. Add TestVMWithStorageNetwork class in integrations/test_3_vm.py, contains 2 TCs:

   • test_enable_storage_network_with_cli_stopped_vm: Main TC
   • test_enable_storage_network_with_api_stopped_vm: Together

2. Add checker fixtures in fixtures/*.py

   • Mainly refer to implementation in e2e rework: test_vm_actions.py #940
   • Handle polling (GET) operations (e.g. while endtime > datetime.now():...) to reduce duplicate code.

3. Refactor related storage-network integration TCs by checkers

   • test_0_storage_network.py::test_storage_network
   • test_1_images.py::TestImageWithStorageNetwork

Special notes for your reviewer:

1. For new checkers, I refer to e2e rework: test_vm_actions.py #940 but temporarily w/o callback behavior to just handle explicit polling operations.

Additional documentation or context

Verification

1. 🟢 harvester-install-and-test#58 using single node v1.3.1

   

2. 🟢 Local ipxe-example using 3 nodes v1.2.1