Consider adding isolated scopes - requesting feedback

> [!IMPORTANT]
> Not sure if we want/need to do this yet - depends if there's enough demand from the community. Add a thumbs up or something here if you really really want this!

### Description

From [this discord thread](https://discord.com/channels/621778831602221064/1410312909313020035/1410312909313020035), the SDK user is looking for a way to "Push" a scope with some tags etc. that only get applied to events captured in a certain context (e.g. the code to handle a particular button press).

This currently isn't possible in Global Mode (which we recommend for Desktop/Mobile apps) because it doesn't allow you to push new scopes:
https://github.com/getsentry/sentry-dotnet/blob/6e50eaa87b3aa24a921824c4494566b01f0640f0/src/Sentry/Internal/SentryScopeManager.cs#L75-L79

One solution would be to add something like Isolated scopes (which we have in the JS SDK) that could be created in GlobalMode.