fix(tracing): Set sample rate in transaction metadata and DSC

[Lms24]

Set the transaction.metadata.transactionSampling.rate field to 1 or 0 depending on transaction.sampled (if it is defined)

Fixes #5690

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.42 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	60.08 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	17.99 KB (+0.01% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	52.94 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	19.79 KB (0%)
@sentry/browser - Webpack (minified)	64.33 KB (0%)
@sentry/react - Webpack (gzipped + minified)	19.81 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	44.67 KB (+0.01% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.92 KB (+0.03% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.29 KB (+0.03% 🔺)