Deadlock and concurrent modification related to Model.data

[jinliu9508]

Description

One Line Summary

Fix ANR and concurrent modification exception related to Model.setOptAnyProperty that locks Model.data.

Details

Motivation

Fix a bug that causes ANR and/or concurrent modification exception

Scope

This will solve any ANR that calls setOptAnyProperty and concurrent modification exception that calls toJson in the stack trace.

Other

This PR comprises three commits. The first commit introduces a test unit that creates a deadlock scenario, resulting in a failed test due to the deadlock. The second commit implements the fix for the issue, allowing us to observe the successful execution of the unit test post-fix. The third commit concludes with final wrap-up and cleanup, preparing it for merging.

Testing

Unit testing

A test unit is added to SubscriptionManagerTests to simulate a deadlock scenario.

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

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This change is 

[jkasten2]

I see some other possible deadlocks, such as addItem and removeItem since they fire events externally. Even if firing doesn't create a deadlock now this is a risk in the future, as well threads could be waiting longer than needed.