Respect duration since last iam trigger when the app is quit and relaunched

[emawby]

Description

One Line Summary

This PR fixes an issue where we were not previously respecting the duration since last IAM trigger if the app was closed and relaunched.

Details

The duration since last IAM time stamp was not being persisted to SharedPreferences meaning that it is reset if the app is closed and relaunched. This PR persists that time stamp to SharedPreferences when an IAM is dismissed and fetches it when initializing the OSInAppMessageController class.

The time stamp is persisted as a string using the format of the Date class's toString() method:
EEE MMM dd HH:mm:ss zzz yyyy

Motivation

Fix a bug

Testing

Unit testing

When do not currently have the infrastructure to test this kind of IAM persistence in unit tests

Manual testing

I tested this on an Android device and emulator.

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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This change is 

[jkasten2]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Jeasmine and @nan-li)