fix(lint/status): compute experimental status from core browser set

[caugner]

Summary

Updates the status lint to compute the experimental status from the core browser set (as defined by Baseline).

Test results and supporting details

See: https://github.com/web-platform-dx/web-features/blob/main/docs/baseline.md#core-browser-set

Related issues

Unblocks https://github.com/mdn/browser-compat-data/pull/28592 (see this review thread).

[github-actions[bot]]

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