Extract the audience utility logic from `Analytics_4` to a new class.

[techanvil]

Feature Description

There is a significant chunk of audience related code that is a prime candidate to lift out of the ever-growing Analytics_4 class into its own class.

We should extract the majority of the linked block of code to a new class called Analytics_4/Audiences which can be used within the Analytics_4 class.

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

• Audience utility methods should be lifted out of the Analytics_4 class as per the feature description.

Implementation Brief

• [ ]

Test Coverage

QA Brief

Changelog entry