Make swiftAsyncStacktraces GA

[philprime]

Description

The optionswiftAsyncStacktraces is experimental https://github.com/getsentry/sentry-cocoa/blob/98f170378ec031b328ed6a027f20aa6bd9189f92/Sources/Swift/Options.swift#L576-L582

When enabled the SentryCrashStackCursor_SelfThread uses backtrace_async instead of backtrace, which uses Swift async stitching, meaning you get better stacktraces when using Swift async.

We have to validate that this feature works correctly. If it does, using backtrace_async should be the default, and we should remove the experimental option, as the docs claim that it behaves exactly like backtrace; see https://manp.gs/mac/3/backtrace

We already track adoption with the SentryEnabledFeaturesBuilder

https://github.com/getsentry/sentry-cocoa/blob/98f170378ec031b328ed6a027f20aa6bd9189f92/Sources/Swift/Helper/SentryEnabledFeaturesBuilder.swift#L21-L23

[linear[bot]]

COCOA-1040

[philipphofmann]

I removed this issue from the 10.0 project because first we should make it GA. Then we can consider turning on by default in 10.0 if it works correctly. So when completing this issue, we must create a follow up issue to consider turning this on by default in 10.0.