ref(core): Make remaining client methods required

[mydea]

This makes the following required on the client:

• captureSession
• getSdkMetadata
• addEventProcessor
• getEventProcessor
• getIntegrationByName
• addIntegration
• init
• captureAggregrateMetrics

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	77.82 KB (-0.35% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	69.04 KB (-0.36% 🔽)
@sentry/browser (incl. Tracing, Replay with Canvas) - Webpack (gzipped)	72.97 KB (-0.36% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	62.67 KB (-0.43% 🔽)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	33.21 KB (-0.17% 🔽)
@sentry/browser (incl. browserTracingIntegration) - Webpack (gzipped)	33.08 KB (-0.18% 🔽)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	31.11 KB (-0.15% 🔽)
@sentry/browser (incl. sendFeedback) - Webpack (gzipped)	31.1 KB (-0.16% 🔽)
@sentry/browser - Webpack (gzipped)	22.36 KB (-0.19% 🔽)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	75.81 KB (-0.34% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	67.35 KB (-0.37% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	33.31 KB (-0.18% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped)	24.41 KB (-0.2% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	212.15 KB (-0.5% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	100.77 KB (-0.27% 🔽)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	73.18 KB (-0.33% 🔽)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	36.49 KB (-0.14% 🔽)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	69.42 KB (-0.38% 🔽)
@sentry/react - Webpack (gzipped)	22.42 KB (-0.17% 🔽)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	87.16 KB (-0.31% 🔽)
@sentry/nextjs Client - Webpack (gzipped)	50.29 KB (-0.13% 🔽)
@sentry-internal/feedback - Webpack (gzipped)	17.1 KB (-0.1% 🔽)