feat(unified-react-native): add unified-react-native support

[Mercy811]

Summary

• Add the new @amplitude/unified-react-native beta package.
• Initialize Analytics, Experiment, Session Replay, and Guides and Surveys through initAll.
• Share serverZone, instanceName, and translated logLevel defaults while allowing blade-specific overrides.
• Expose Experiment, Session Replay, and Guides and Surveys accessors alongside the React Native Analytics API.
• Ship a React Native CLI autolinking preset so applications directly install only the unified package.
• Add a bare React Native example that consumes the one-package preset and exercises every blade.
• Add package documentation, build configuration, and full unit coverage.

Stacked on #1944, which provides @amplitude/plugin-experiment-react-native.

Testing

• pnpm install --frozen-lockfile
• Unified React Native build, typecheck, lint, and tests (18 tests, 100% coverage)
• Unified example lint and typecheck
• React Native CLI config resolves all five transitive native dependencies for iOS and Android
• Android :app:generateAutolinkingPackageList
• iOS pod install (five native modules plus Engagement and AsyncStorage codegen)
• Production iOS Metro bundle
• pnpm docs:check
• pnpm lint
• pnpm lint:deps
• pnpm test (30 projects)
• pnpm build — the new package and its dependencies build successfully, but the repository-wide command stalls in the unrelated @amplitude/segment-session-replay-plugin Rollup task
• pnpm test:examples — the base branch references a missing root jest.setup.examples.js

Checklist

• PR title follows the conventional commit format
• Breaking change: No

[linear-code]

SDKRN-61

[github-actions]

size-limit report 📦

Path	Size
packages/analytics-browser/lib/scripts/amplitude-min.js.gz	61.58 KB (+0.07% 🔺)
packages/session-replay-browser/lib/scripts/session-replay-browser-min.js.gz	134.97 KB (0%)
packages/unified/lib/scripts/amplitude-min.umd.js.gz	215.62 KB (+0.02% 🔺)
@amplitude/element-selector (gzipped esm)	2.67 KB (0%)