feat: implement activity dot indicator experiment

[anandaroop]

This PR resolves ONYX-1465

Description

Sets up the activity dot experiment

• Fire the experiment_viewed event (only once per session?)

Control	Variant B	Variant C

TODO:

PR Checklist

• I have tested my changes on iOS and Android.
• I hid my changes behind a feature flag, or they don't need one.
• I have included screenshots or videos, or I have not changed the UI.
• I have added tests, or my changes don't require any.
• I added an app state migration, or my changes do not require one.
• I have documented any follow-up work that this PR will require, or it does not require any.
• I have added a changelog entry below, or my changes do not require one.

To the reviewers 👀

• I would like at least one of the reviewers to run this PR on the simulator or device.

Changelog updates

Changelog updates

Cross-platform user-facing changes

iOS user-facing changes

Android user-facing changes

Dev changes

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