OCPNODE-4623: e2e for Block runc on RHEL 10 via OSImageURL stream class inspection

[asahay19]

Summary

This PR adds disruptive e2e coverage for the osImageURL runc-on-RHEL-10 guard (OCPNODE-4518 / MCO stream-class inspection), in the existing runc RHCOS 10 upgrade guard suite alongside the osImageStream cases.

The new test verifies that when a pool uses runc via ContainerRuntimeConfig and targets RHCOS 10 through a MachineConfig osImageURL override (with no MachineConfigPool.spec.osImageStream), MCO blocks at render time (RenderDegraded), sets cluster upgradeability to Upgradeable=False, and leaves the node on RHCOS 9 with runc.

Key design points:

• MCP omits osImageStream entirely — osImageURL and osImageStream on the same pool are mutually exclusive and produce a different render error, not the runc guard.
• Guard assertion matches MCO’s message: targets a RHEL 10 OS image where runc is not available; fails fast if the stream+URL conflict message appears instead.
• On clusters whose OSImageStream default is rhel-10, the test temporarily pins RHCOS 9 via a baseline osImageURL MC, removes it, then applies the RHEL 10 URL so only one user URL MC is active at guard time.

Summary by CodeRabbit

• Tests

  • Added coverage for RHEL 9-to-10 upgrades using osImageURL when runc is the default runtime.
  • Verifies upgrades are blocked, rendering enters the expected degraded state, and nodes remain ready without an unintended rollout.
  • Added cleanup and validation for temporary upgrade configurations and machine settings.

• Documentation

  • Documented the separate osImageURL upgrade-guard scenario, expected behavior, configuration constraints, and related references.