fix: fail closed when draining CN pipelines

[loveRhythm1990]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

Fixes #616

Related to matrixorigin/matrixone#27776

What this PR does / why we need it:

During CNClaim migration, a source CN can still be executing remote pipelines after its ordinary frontend sessions reach zero. The operator did not enable GetPipelineInfo for verified MO 3.x and 4.x releases, so those pipelines could be treated as zero and the source CN could be reclaimed early.

This change:

• enables PipelineInfo for the verified MO 3.x and 4.x release lines;
• records whether session, pipeline, and replica counts were successfully observed in the current refresh;
• invalidates observation evidence before each refresh so failed or partial queries cannot reuse an old zero;
• treats legacy score annotations as unsafe until a fresh observation succeeds;
• requires all observations needed by the current MO version to be both current and zero before normal reclaim;
• preserves the existing force-timeout, unsupported-version, and CN-absent-from-HAKeeper behavior.

Special notes for your reviewer:

The feature gate intentionally remains explicit per MO major release. Unknown or unverified major versions retain the existing compatibility behavior and do not enable version-specific RPCs.

No end-to-end test was run locally. Static diff validation passed, and 62 tests in api/core/v1alpha1 and pkg/controllers/common passed. The cnstore test binary cannot be linked on the local macOS environment because libmo is unavailable; CI should run the full suite in the project build environment.

Additional documentation:

The incident mechanism and acceptance criteria are documented in #616.

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