Add creating state to GraphQL enum and frontend for SPEP test runs

What does this MR do and why?

Adds the CREATING state to the GraphQL enum and frontend for SPEP (Scheduled Pipeline Execution Policy) test runs.

This is part of a two-MR rollout to add atomic state transitions for test run pipeline creation:

1. This MR (frontend-first): Add CREATING state to GraphQL enum and frontend
2. !244864 (merged) (backend): Add creating state to model and implement atomic state transition in worker

Why deploy frontend first?

The frontend handles unknown states gracefully via DEFAULT_TEST_RUN_CONFIG fallback, so deploying this first is safe. Once merged, the backend MR can be deployed to start using the new state.

Changes

• Add CREATING value to PolicyScheduleTestRunStateEnum GraphQL enum
• Add CREATING to frontend TEST_RUN_STATES constant
• Add badge config for CREATING state (info variant, pending icon, "Creating pipeline" text)
• Update isTestRunActive to include CREATING state (keeps subscription active during pipeline creation)
• Add test coverage for new state

References

• Backend MR: !244864 (merged)
• Issue: #591425 (closed)

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