pkg/cache/scheduler: add exclusion stats to TAS failure messages

[sohankunkerkar]

Include detailed node exclusion reasons (taints, nodeSelector, affinity, resources) in TAS scheduling failure messages to improve debuggability.

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #7854

Special notes for your reviewer:

Does this PR introduce a user-facing change?

TAS: extend the information in condition messages and events about nodes excluded from calculating the
assignment due to various recognized reasons like: taints, node affinity, node resource constraints.

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[Copilot]

Pull request overview

This PR enhances TAS (Topology Aware Scheduling) failure messages by adding detailed node exclusion statistics. When scheduling fails, users will now see why nodes were excluded (e.g., taints, nodeSelector mismatches, affinity rules, insufficient resources) along with counts for each exclusion reason.

Key Changes:

• Introduced ExclusionStats to track and report node exclusion reasons during TAS scheduling
• Enhanced failure messages to include total node count and breakdown of exclusion reasons
• Updated 30+ test cases to validate the new detailed error messages

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pkg/cache/scheduler/tas_flavor_snapshot.go	Core implementation: Added ExclusionStats struct, limitingResource function for identifying bottleneck resources, and updated fillInCounts/notFitMessage to track and format exclusion statistics
pkg/scheduler/scheduler_tas_test.go	Updated 16 test cases to match new detailed failure message format with exclusion statistics
pkg/cache/scheduler/tas_cache_test.go	Updated 14 test cases and added 2 new test cases to validate exclusion stats formatting and resource bottleneck detection

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[mimowo]

LGTM overall, I love this PR, this will greatly improve debuggability.

It does not change the API other than messages so I would like to backport it.

cc @PBundyra @pajakd @mwysokin

[mimowo]

/remove-kind cleanup
/kind feature
/release-note-edit

TAS: extend the information in condition messages and events about nodes excluded from calculating the
assignment due to various recognized reasons like: taints, node affinity, node resource constraints.