Application mode Sessions by default (between Init and Close)

[bruno-garcia]

Sentry Native introduced a session mode called "application mode session". It's defined by a session which starts when the SDK is initialized and it ends when the process exits.

Docs for it are here: https://docs.sentry.io/platforms/native/configuration/releases/#release-health

typically just a single session from application start to quit

More on the spec: https://develop.sentry.dev/sdk/sessions/

We need to make sure that:

• Add an option: EnableAutoSessionTracking with default false until our next major, where we'll flip the default to true.
• Unhandled exceptions (marked as handled: false) finish the session as crashed.
• When the SDK is disposed, sessions are closed