Grouping: Improve grouping for App Hangs only having one main in-app frame #101238
Description
A customer in getsentry/sentry-cocoa#6345 and also in an internal customer case in Notion both reported that app hangs only having one in-app frame with main are grouped into the same group, which makes it really hard to debug them.
While getsentry/sentry-cocoa#6345 surfaced that most of these app hangs stem from false positives, which we are going to fix with getsentry/sentry-cocoa#6381, it still can occur that the app hangs with only one in-app frame that is main. In that case we must group differently. One idea is to group by all frames for app hangs when they only have one in app frame that is main.