Native integration: cache directory path

Native backend uses offline caching to store the error at the time of the crash and only sends it later on the second app run. what do we want to do about the cache directory path? Defaults to the current working directory. Can we figure out a more reasonable default or do we want to document this? Or even warn unless explicitly specified?

> See [https://github.com/getsentry/sentry-dotnet/pull/2887#issuecomment-1830328182]()
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> > what do we want to do about the cache directory path? Defaults to the current working directory. Can we figure out a more reasonable default or do we want to document this? Or even warn unless explicitly specified?
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> This is a problem on a Mac where the OS asks the user to give permission if the file is on Documents and others.
I wonder if using a consistent path name under `Path.GetTempPath` is an alternative.
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> It's a problem on Unity today btw ^ so we could align the solution here
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> ALso a problem the fact we don't have paths by default. And the .NET SDK doesn't support having more than 1 instance of the app running at the same time (afaik not fixed) as worker transports would race to pick work off of the directory