fix: call all revalidators per key to respect individual isPaused() states

[dcondrey]

Summary

Fixes #2333 — when multiple components consume the same SWR key with different isPaused() configurations, only revalidators[0] was called during event revalidation. If that first revalidator belonged to a paused hook, all other (unpaused) hooks were blocked from revalidating.

• src/index/use-swr.ts: Extract triggerRevalidators() helper that iterates all registered revalidators for error retry events instead of calling only revalidators[0]
• src/_internal/utils/mutate.ts: Call all revalidators on MUTATE_EVENT with { dedupe: true } so every hook gets a chance to participate while avoiding redundant fetches
• test/use-swr-revalidate.test.tsx: Add tests for multi-hook isPaused scenarios, mutate with shared keys, and error retry with multiple hooks

Test plan

• Existing test suite passes (no regressions)
• New test: multiple hooks sharing a key where one has isPaused: () => true — the unpaused hook still revalidates
• New test: mutate() triggers all revalidators for a shared key with deduplication
• New test: error retry calls all revalidators so recovery propagates to all hooks

[codesandbox-ci]

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