feat(replay): Add getReplayId() method

[mydea]

This adds a public getReplayId() method to the replay integration to get the ID of the ongoing session.

Closes#7795

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.98 KB (+0.07% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	65.56 KB (+0.05% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.53 KB (+0.09% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	58 KB (+0.05% 🔺)
@sentry/browser - Webpack (gzipped + minified)	21.13 KB (+0.07% 🔺)
@sentry/browser - Webpack (minified)	68.95 KB (+0.04% 🔺)
@sentry/react - Webpack (gzipped + minified)	21.15 KB (+0.07% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	48.95 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	28.54 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.77 KB (+0.06% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	44.93 KB (+0.04% 🔺)
@sentry/replay - Webpack (gzipped + minified)	38.86 KB (+0.04% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	63.82 KB (+0.05% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	56.86 KB (+0.05% 🔺)

[pckilgore]

Doesn't directly address my issue because I still manually need to construct URLs with the IDs, but helpful nonetheless, thank you!

[mydea]

Doesn't directly address my issue because I still manually need to construct URLs with the IDs, but helpful nonetheless, thank you!

Yeah, the idea is to unblock this with a public API (building the URL is tricky as we don't necessarily know about where the UI is hosted etc). To at least enable to do this yourself without using private APIs!