feat(license): invalidate license when cpu exceeds limit instead of rejecting new compute nodes from joining

[BugenZhao]

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What's changed and what's your intention?

In #18022, we introduced CPU core limit for license keys, where we would reject new compute nodes from joining the cluster if the limit was exceeded. This led to some confusing behavior like #18401.

In this PR, we modify the behavior so that the license key is temporarily invalidated (thus all Paid features unavailable) when the CPU exceeds its limit. This requires the information of "cluster size" is broadcast to all worker nodes. For simplicity, a new notification variant of compute_node_total_cpu_count is introduced, instead of maintaining the complete worker node meta data.

The benefit is that, the check for CPU limit is deferred until a paid feature is actually used, and scaling out the cluster won't trigger a hard error any more. If the user isn't utilizing any paid features, they may not even notice this limit. This may enable us to offer a default 'Paid' license key with a small CPU limit in production, helping users better investigate and demonstrate our product.

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• My PR contains critical fixes that are necessary to be merged into the latest release.

Documentation

• My PR needs documentation updates.

Release note

[fuyufjh]

LGTM

[gru-agent]

This pull request has been modified. If you want me to regenerate unit test for any of the files related, please find the file in "Files Changed" tab and add a comment @gru-agent. (The github "Comment on this file" feature is in the upper right corner of each file in "Files Changed" tab.)

[BugenZhao]

• feat(license): set default key in production to enable paid features in clusters with a maximum of 4 CPU cores #20296
• feat(license): invalidate license when cpu exceeds limit instead of rejecting new compute nodes from joining #20276 👈 (View in Graphite)
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