Tracks saving flow should persist

[achou11]

PR comment with original context located here

When in the flow of saving a track, there's a chance that the app may quite unexpectedly or the user leaves it unintentionally. In order to avoid lost information, we want to have a similar pattern to what we do with observations, where we persist information to local storage (we mmkv via zustand persist) and read that on initial app load to determine if there was an "in-progress" track being saved.

Changes needed:

• Update the zustand store used for tracks to use persist the relevant tracks information (e.g. locationHistory). see createPersistedState.ts
• update AppNavigator.tsx to load an existing track as the initial route for the navigator if it exists and if the feature flag is enabled. See implementation in that file for observations as an example
  • in this specific case, the save behavior of the Saving Track screen should reset the navigation state so that the screen cannot be returned to afterwards (e.g. back button/gesture).