Propagate changes in app.isLaunching to the NDK layer

[fractalwrench]

Goal

Currently app.isLaunching is only set on JVM error reports. This changeset adds it to NDK error reports and adds verification that it has been set for both in the form of E2E tests.

Changeset

• LaunchCrashTracker extends BaseObservable and notifies its observers when isLaunching is set to false
• The NativeBridge which communicates with the NDK layer invokes a JNI function which updates bsg_event->app.is_launching to false
• Fixed JVM serialization bug where inForeground rather than isLaunching value was serialized
• Added is_launching to bsg_app_info struct
• Added bugsnag_app_get_is_launching/bugsnag_app_set_is_launching functions to allow users to alter the value in an on_error callback.

Struct migration

When a fatal NDK error occurs, the memory contents of bsg_event struct is persisted on disk and then loaded again the next launch. Because the struct can change between releases, old payloads need to be migrated to the new struct. This has been achieved by the following changes:

• Check whether BUGSNAG_EVENT_VERSION is 4 and load it into bugsnag_report_v4, which is a copy of the previous struct definition
• Check the BUGSNAG_EVENT_VERSION in the serializer and migrated the bsg_app_info values
• Set a default value for app.is_launching to false if no information was available in the struct

Testing

• Added/updated unit test coverage where appropriate, particularly for migrating the struct
• Verified that app.isLaunching is set appropriately in JVM/NDK E2E tests

[twometresteve]

LGTM so long as @kstenerud is now happy.