Expose top-level Sentry.setAttribute / Sentry.setAttributes for API parity with core

[antonis]

@sentry/core 10.61.0 added top-level Sentry.setAttribute(key, value) and Sentry.setAttributes(attrs) APIs (getsentry/sentry-javascript#21705). The RN SDK re-exports core via an explicit allowlist (packages/core/src/js/index.ts), so these are not currently exposed to RN users.

This is a low-priority parity enhancement, not a bug — RN users can already call getCurrentScope().setAttribute(...), which works and syncs to native today.

Why it's safe/cheap: the new functions delegate to getIsolationScope().setAttribute(s), and RN already patches the isolation scope (enableSyncToNative(getIsolationScope()) in sdk.tsx) to forward primitive attributes to native. So exposing them gets native scope-sync for free — no extra wiring.

Scope of work:

• Add setAttribute, setAttributes to the export { … } from '@sentry/core' block in packages/core/src/js/index.ts
• Regenerate API report (yarn build:sdk && yarn api-report)
• Add a test asserting Sentry.setAttribute('k', 'v') forwards to NATIVE.setAttribute (isolation-scope → native path)
• CHANGELOG entry
• Note: only primitive values sync to native (existing scopeSync behavior)

[linear-code]

RN-689