Add Live Activities support

[nan-li]

Description

One Line Summary

Adds Live Activity support.

Details

Motivation

Adding 2 SDK methods that allow a customer to register their temporary live activity token with an activity ID on OneSignal's backend:

1. enterLiveActivity
2. exitLiveActivity

Scope

Adding bridging to access the two iOS SDK methods.

Testing

Unit testing

The iOS repo contains tests, this is only bridging

Manual testing

Testing limited since no real push token is available.

• Tested that the Flutter example app can call these two methods and receive the onFailure response with a correct 404 error.

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
• 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.
• I have reviewed this PR myself, ensuring it meets each checklist item

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This change is 

[jkasten2]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @nan-li)

[fhboswell]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @nan-li)