Add pytest-based CI test framework v2 with ephemeral namespace isolation

[ddjain]

Description

Introduce a new CI test framework (tests_v2) using pytest with:

• Ephemeral namespace per test for isolation
• Scenario-based layout (e.g. pod_disruption, application_outage)
• Makefile + setup script for local/CI runs
• Dedicated GitHub workflow for v2 tests

Goal: improve maintainability and isolation of functional tests compared to the current CI tests.

[ddjain]

Migration plan: All existing v1 tests will be migrated to the v2 framework. For each scenario or test group migrated, a separate GitHub issue will be created so migration work can be tracked and reviewed independently.