ref: Export Session class from core/browser/node

[kamilogorek]

This makes it possible to write hub-less code like:

const release = `${inputs.repo}@${inputs.version}`;
const client = new Sentry.NodeClient({
  dsn: process.env.SENTRY_DSN,
  release
});
const session = new Sentry.Session({
  status: 'crashed',
  release
});

client.captureMessage(`Release failed: ${inputs.repo}`);
client.captureSession(session);

instead of going through const session = Sentry.getCurrentHub().startSession({ ... })

[github-actions]

size-limit report

Path	Base Size (d898730)	Current Size	Change
@sentry/browser - CDN Bundle (gzipped)	19.68 KB	19.69 KB	+0.04% 🔺
@sentry/browser - CDN Bundle (minified)	62.89 KB	62.91 KB	+0.03% 🔺
@sentry/browser - Webpack	22.21 KB	22.21 KB	0%
@sentry/browser - Webpack - gzip = false	76.02 KB	76.02 KB	0%
@sentry/react - Webpack	22.24 KB	22.24 KB	0%
@sentry/nextjs Client - Webpack	46.24 KB	46.31 KB	+0.17% 🔺
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	28.22 KB	28.23 KB	+0.02% 🔺