feat(tracing): Allow to set instrumenter on Span & Transaction

[mydea]

A span & transaction now have a field instrumenter that can be used to check where a the span/transaction was created.
This defaults to sentry.

In later steps, we can use this information to react internally based on SDK config.

ref #6127

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.49 KB (0%)
@sentry/browser - ES5 CDN Bundle (minified)	60.35 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.12 KB (+0.01% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	53.67 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	19.86 KB (0%)
@sentry/browser - Webpack (minified)	65.12 KB (0%)
@sentry/react - Webpack (gzipped + minified)	19.88 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	45.81 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.26 KB (+0.09% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.65 KB (+0.13% 🔺)

[Lms24]

LGTM!